Pituitary neuroendocrine tumors: a model for neuroendocrine tumor classification

Understanding the Mechanical Properties of Pituitary Adenomas for Optimized Surgery

Pituitary adenoma (PA) is a common brain tumor located in a small cavity at the cranial base. It disrupts hormonal balance and compresses the optic nerves, leading to abnormal body growth, sexual dysfunction, vision loss, and mortality if untreated. Its surgical resection is highly challenging due to its small size, heterogeneous structure, deep location, and indistinct interface with surrounding nerves, arteries, and brain tissues. Mechanical properties of tumor tissues play a crucial role in their microstructure, growth, and progression. However, data on the mechanical properties of PA tissues is scarce. This study aims to provide detailed mechanical properties of various PA tissues and demonstrate the differences in stiffness between tumors and brain tissues. The viscoelastic properties and collagen content of postoperative PA tissues (n = 40) and normal human brain white matter (n = 7) were analyzed using in vitro nanoindentation and histological staining, respectively. Tumor consistency was also assessed preoperatively via magnetic resonance images (MRIs) and intraoperatively through surgeon feedback. PA tissues exhibited a considerable variation in viscoelastic properties; however, their average stiffness was significantly higher than normal brain white matter (p < 0.05). Tumors with firm consistency showed higher collagen content (29.8%± $$ \pm $$ 21.2%) than the soft (9.1%± $$ \pm $$ 8.1%) and medium (12.9%± $$ \pm $$ 9.7%) consistency tumors, however the correlation with mechanical properties was not strong (r = 0.40, p = 0.01). Strong correlations between preoperative predictions, intraoperative observations, and postoperative measurements emphasize the clinical relevance of these findings. These results underscore the potential of mechanical biomarkers to enhance surgical strategies, improve outcomes, and support applications in diagnosis, development of elastography and elastic image fusion algorithms, as well as in robot-assisted interventions.

Clinicopathological Correlates of Hormone Expression-Based Subtypes of Non-Functioning Duodenal/Ampullary Neuroendocrine Tumors: A Multicenter Study of 151 Cases

Duodenal neuroendocrine tumors (Duo-NETs) may arise in the ampullary and non-ampullary duodenum. Non-functioning Duo-NETs (NF-Duo-NETs), which account for most cases, may express various hormones. Previous studies have suggested that hormone production might be associated with biological aggressiveness. Current treatment protocols are based on functionality, tumor size, and location, but small NF-Duo-NETs may also have metastatic potential. We aimed to investigate whether tumor cell subtyping, based on hormone expression, could provide further insights into NF-Duo-NET biological behavior. We analyzed the clinico-pathological correlates of hormone expression in a multicenter series of 151 NF-Duo-NETs, subdividing tumors into five subtypes: gastrin-producing G-cell NETs (Gas-NETs), somatostatin-producing D-cell NETs (Som-NETs), serotonin-producing enterochromaffin-cell NETs (Ser-NETs), plurihormonal NETs, and gastrin-, somatostatin-, and serotonin-negative NETs (GSSN-NETs). Som-NETs were the most frequent (31%), followed by plurihormonal NETs (26%), Gas-NETs (24%), GSSN-NETs (13%), and Ser-NETs (4%). Som-NETs and GSSN-NETs were more commonly located in the ampullary region and showed significantly larger size, more frequent lymphatic and/or vascular invasion, and higher pT, pN, and American Joint Committee on Cancer (AJCC-9th edition) stages compared to Gas-NETs, which were often (77%) diagnosed at AJCC stage I. Ampullary Som-NETs showed a more invasive and metastatic potential compared to non-ampullary Som-NETs, while, among plurihormonal NETs, the predominantly expressed hormone influenced tumor biological features, with gastrin-predominant NETs showing less invasive potential. At logistic regression, both tumor cell subtype and tumor size were independently associated with aggressiveness (pT3, pN1, or pM1 stage at diagnosis). Hormonal expression profiling may be clinically relevant in NF-Duo-NETs, independently of tumor size.

Cabergoline-induced NDFIP1 upregulation in pituitary neuroendocrine tumor cells activates mTOR signaling and contributes to cabergoline resistance

PURPOSE

To investigate the molecular mechanisms underlying resistance to dopamine agonists (DA).

METHODS

LC-MS/MS analysis was performed on rat pituitary neuroendocrine tumors (PitNET) cell line GH3 to identify differentially expressed proteins induced by cabergoline (CAB) treatment. A total of 180 human PITNET samples were subjected to transcriptome analysis. Immunohistochemistry (IHC) was conducted on 29 tumor samples to validate NDFIP1 alteration. A xenograft mouse model was established by subcutaneously injecting GH3 cells, with or without NDFIP1 overexpression, into nude mice to investigate tumor growth. PitNET cell lines were treated with CAB. Cell proliferation was assessed using the CCK-8, and protein expression levels were examined through Western blot analysis.

RESULTS

CAB treatment upregulated FDFT1 and NDFIP1 protein expression in GH3 cells, with NDFIP1 showing a significant positive correlation with tumor size, as confirmed by IHC results. MMQ and GH3 cells overexpressing NDFIP1 exhibited enhanced viability and reduced sensitivity to CAB. In vivo experiments demonstrated that subcutaneous injection of NDFIP1-overexpressing GH3 cells led to enhanced tumor growth compared to parental GH3 cells. Although the total levels of PTEN remained unaltered, NDFIP1 overexpression induced PTEN nuclear translocation, potentially activating the mTOR pathway. This was supported by increased phosphorylation of key mTOR pathway components, including p-AKT and p-4EBP1, in cells overexpressing NDFIP1.

CONCLUSION

CAB treatment induces the upregulation of NDFIP1 in PitNET cells, which correlates with tumor size and contributes to reduced CAB sensitivity, potentially through activation of the mTOR pathway. NDFIP1 as a potential therapeutic target for overcoming DA resistance in PitNET patients.

Non-recurrent mutations and copy number changes predominate pituitary adenoma genomes

OBJECTIVE

Pituitary adenomas (PAs) are common neoplasms. Our current understanding of the molecular basis of PA formation is incomplete. Routine implementation of targeted genomics has enabled the discovery of rare, potentially clinically actionable events.

METHODS

We used a cancer-focused gene panel to sequence a cohort of 171 PAs from patients who underwent surgery at Brigham and Women's Hospital from 2012 to 2020.

RESULTS

We identified known genetic variants enriched in specific PA subtypes: GNAS (somatotroph) and USP8 (Cushing's disease). Total mutational burden did not vary across adenoma subtypes; most adenomas possessed a few non-recurrent mutations in various established oncogenes and tumor suppressors. In contrast, the burden of copy number alterations varied widely across adenoma subtypes and was associated with higher MIB1 labeling index. We identified frequent deletions spanning MEN1 in prolactinomas and silent corticotroph adenomas, and subtype-specific copy number changes including 16p, 16q alterations in somatotroph adenomas without GNAS mutations. Within the corticotroph lineage, adenomas leading to Cushing's disease had few copy number alterations while silent corticotroph adenomas had numerous.

CONCLUSIONS

This study highlights a role for individualized genetic events in PA formation and suggests that divergent patterns of genomic instability may facilitate tumorigenesis even within the same lineage. Taken together, we demonstrate how gene panels may illuminate novel biology in endocrine tumors.

Comprehensive Classification of Surgically Resected Pituitary Neuroendocrine Tumors: Updates From a Single-Institution Experience Based on the WHO 5th Edition

BACKGROUND

The 5th edition of WHO classification (WHO5) renamed pituitary adenoma as pituitary neuroendocrine tumor (PitNET), aligning with NET nomenclature from other sites. This study investigated the clinicopathological characteristics of surgically resected PitNET based on the WHO5 classification.

METHODS

A retrospective analysis was conducted on 210 cases of surgically resected and pathologically confirmed PitNET treated at Seoul National University Hospital from 2021 to 2023. The tumors were graded using the French five-tiered grading system proposed by Trouillas et al. Detailed information on grade 3 metastatic PitNET cases is provided.

RESULTS

The cohort's median age was 53 years (age range: 8-84 years), with a male-to-female ratio of 1:1.1. Mean tumor size was 2.5 cm (range: 0.1-6.5 cm). Macroadenomas predominated (91.9%), followed by microadenoma (6.7%), and giant tumors (1.4%), with 56.2% extending suprasellarly. SF1-lineage PitNET was most prevalent (49.5%), followed by PIT1-lineage (23.3%) and TPIT-lineage (17.1%). Null cell tumors (5.7%) and unclassified plurihormonal PitNET (4.3%) were rare. PIT1-lineage PitNET comprised somatotrophs (47.0%), mature plurihormonal PIT1 lineage tumors (18.4%), thyrotrophs (16.3%), immature PIT1-lineage tumors (16.3%), and acidophilic stem cell tumors (n=1), however, there was no lactotroph PitNET. Among SF1-lineage tumors, serologically non-functional tumors predominated (79%), while, immunohistochemically, 71.2% were gonadotrophin (FSH/LH)-positive. Tumor grades by the French five-tiered classification system were distributed as follows: grade 1a (58.1%), 1b (17.6%), 2a (16.2%), 2b (7.1%), and 3 (1.0%). Two cases of metastatic corticotroph PitNET were observed: The first case, a 50-year-old female had liver metastasis and experienced tumor recurrence 7 years after his initial diagnosis of PitNET, ultimately dying 9.5 years later. The primary tumor appeared bland, but the metastatic tumor exhibited a high mitotic rate and a Ki-67 index was 48%. The second case involved a 44-year-old man with metastases to the paranasal sinus, liver, and bone. Despite showing initial bland histopathology and a low proliferation index, this tumor displayed aggressive behavior. The patient had a recurrence 1.5 years after diagnosis, with additional metastases emerging 3 years later. He survived for 8.0 years and is currently disease-free following surgery, chemotherapy, and radiotherapy.

CONCLUSION

This comprehensive analysis of surgically resected PitNETs using the new WHO5 classification provides valuable insights into the distribution of the subtypes in the surgical cohort. Key findings were the predominant gonadotroph PitNET, the absence of lactotroph PitNET, and the rarity of null cell tumors in surgical cases. The lack of lactotrophs was mainly due to medical treatment. This study highlights the discrepancy between serological and immunohistochemical findings of SF1-lineage PitNETs. While metastatic PitNET cases showed poor prognosis, the predictive value of the French grading system for PitNET requires further validation through extended follow-up.

Preoperative Prediction of Non-functional Pituitary Neuroendocrine Tumors and Posterior Pituitary Tumors Based on MRI Radiomic Features

Compared to non-functional pituitary neuroendocrine tumors (NF-PitNETs), posterior pituitary tumors (PPTs) require more intraoperative protection of the pituitary stalk and hypothalamus, and their perioperative management is more complex than NF-PitNETs. However, they are difficult to be distinguished via magnetic resonance images (MRI) before operation. Based on clinical features and radiological signature extracted from MRI, this study aims to establish a model for distinguishing NF-PitNETs and PPTs. Preoperative MRI of 110 patients with NF-PitNETs and 55 patients with PPTs were retrospectively obtained. Patients were randomly assigned to the training (n = 110) and validation (n = 55) cohorts in a 2:1 ratio. The lest absolute shrinkage and selection operator (LASSO) algorithm was applied to develop a radiomic signature. Afterwards, an individualized predictive model (nomogram) incorporating radiomic signatures and predictive clinical features was developed. The nomogram's performance was evaluated by calibration and decision curve analyses. Five features derived from contrast-enhanced images were selected using the LASSO algorithm. Based on the mentioned methods, the calculation formula of radiomic score was obtained. The constructed nomogram incorporating radiomic signature and predictive clinical features showed a good calibration and outperformed the clinical features for predicting NF-PitNETs and PPTs (area under the curve [AUC]: 0.937 vs. 0.595 in training cohort [p < 0.001]; 0.907 vs. 0.782 in validation cohort [p = 0.03]). The decision curve shows that the individualized predictive model adds more benefit than clinical feature when the threshold probability ranges from 10 to 100%. Individualized predictive model provides a novel noninvasive imaging biomarker and could be conveniently used to distinguish NF-PitNETs and PPTs, which provides a significant reference for preoperative preparation and intraoperative decision-making.

Clinical and prognostic implications of pituitary macroadenomas (PitNets) grading: a monocentric experience

RATIONALE

Pituitary neuroendocrine tumors (PitNets), also known as pituitary adenomas, are aggressive in 20% of cases, with local invasion, relapse/scarce response to conventional treatment, in the absence of reliable predictive parameters. In 2018, Trouillas et al. proposed a 5-tier clinicopathological classification, not widely validated yet. In the present study we investigated, in a PitNets monocentric series, the correlation between this classification system and features at diagnosis and medium-term clinical and biochemical outcomes.

MATERIALS & METHODS

we retrospectively evaluated 88 consecutive patients (51 M, 50.5±14.7 yrs) with functioning (FPA) or non-functioning pituitary macroadenomas (NFPA), referred to the Endocrine Unit of Messina University Hospital, and operated by the same neurosurgeon in the period 2015-2020. Of each patient we reviewed recorded demographic, clinical, radiological, biochemical data and visual field, both at diagnosis/last follow-up (median 3 ± 1.5 yrs), therapeutical history, and pathological data. Once classified PitNets according to Trouillas et al. grading system, we correlated it to clinico-pathological and hormonal features at diagnosis, and to clinical, biochemical and ophthalmological outcomes at 6 months after surgery and at last follow-up.

RESULTS

According to Trouillas grading system, 38.6% of patients were assigned the 1a grade, 7.9% the 1b, 48.9% and 4.5% the 2a and 2b, respectively. At diagnosis, panhypopituitarism and visual field alterations were more frequent among 2a grade tumors. GH-omas were significantly prevalent among 1a tumors, NFPA among 2a. PitNets with 1a and 2a grade had a better response to single surgery (p < 0.01), while cyberknife stereotactic radiotherapy was needed more frequently in 2a and 2b tumors. Panhypopituitarism/visual field alterations were more frequent among 2a PitNets even after surgery. Ki-67 was positively associated to persistent disease in FPA, while radiological invasion was associated to remnant presence among NFPA.

CONCLUSIONS

Invasive and not-proliferating PitNets (2a) were more frequently associated to impaired pituitary function/visual field before and after surgery. Less proliferating tumors (1a and 2a) were more responsive to surgery. Ki-67 correlated to disease persistence in FPA, while adiuvant radiotherapy was more needed among invasive tumors. Thus, among ≥ 1 cm PitNets, tumor invasion seems to impact on clinico-biochemical outcomes, while Ki-67 proliferation index influences surgical outcomes.

Contributing factors to postoperative surgical site infections in pituitary neuroendocrine tumors undergoing endonasal transsphenoidal resection

Pituitary Neuroendocrine Tumors (PitNETs), often treated via endonasal transsphenoidal resection, present a risk for postoperative surgical site infections (SSIs), including intracranial infections such as meningitis. Identifying the risk factors associated with these infections is crucial for improving surgical outcomes and patient care. A retrospective study was conducted at a medical center from June 2020 to June 2023. The study included 20 patients with postoperative intracranial infections and 50 controls without infections. Inclusion criteria involved adult patients diagnosed with PitNETs who underwent standard endonasal transsphenoidal surgery and provided informed consent. Exclusion criteria included previous neurosurgical procedures, preoperative infections, concurrent severe diseases, or alternative surgical approaches. Diagnostic criteria for intracranial infections were based on clinical, hematological, cerebrospinal fluid, radiological, and microbiological findings. Statistical analyses were performed using IBM SPSS, focusing on univariate and multivariate logistic regression analyses. Univariate analysis showed no significant association of intracranial infections with factors like smoking history, previous craniotomy, operation time, hypertension, preoperative sphenoid sinusitis, BMI, and age. However, postoperative CSF leaks, intracranial pneumocephalus, diabetes mellitus, and tumor extension to the third ventricle were significantly associated with infections. Multivariate logistic regression further confirmed these findings, with significant odds ratios for these factors. The study reveals a significant correlation between postoperative CSF leaks, intracranial pneumocephalus, diabetes mellitus, and tumor extension to the third ventricle with the occurrence of SSIs following endonasal transsphenoidal resection of PitNETs. Microbial analysis revealed Escherichia coli as the most prevalent pathogen in post-surgery infections, with notable antibiotic resistance patterns observed in key bacteria, necessitating careful antibiotic selection. Tailored clinical treatment strategies addressing these risk factors are essential to reduce the incidence of postoperative SSIs and enhance patient safety.

Multilineage Pituitary Neuroendocrine Tumors Expressing TPIT and SF1: A Clinicopathological Series of Six Tumors

Tumors of adenohypophysial hormone-secreting cells, now classified as pituitary neuroendocrine tumors (PitNETs), have been subclassified based on cell differentiation. Normal adenohypophysial cells have three lineages of differentiation driven by the transcription factors PIT1, TPIT, and SF1 which are responsible for the regulation of hormone gene expression; PIT1 drives expression of GH, PRL, and TSH, TPIT is required for POMC expression that gives rise to ACTH, and SF1 is the transcription factor responsible for FSH and LH expression. The vast majority of PitNETs follow these three lineage differentiation pathways but rare PitNETs show either no lineage differentiation or express biomarkers of more than one lineage. The recent WHO classification continued the terminology "plurihormonal" for tumors that have features of more than one lineage but a better term is "multilineage" since some tumors may express more than one lineage-specific transcription factor without the hormones that are driven by those factors. Recent data indicate that tumors with expression of PIT1 and SF1 are the most common multilineage PitNETs. Here we report the existence of rare PitNETs that express TPIT and SF1. The 6 patients (5 female, 1 male; mean age 54.8 years; range 35-84 years) represent less than 1% of patients in our series of PitNETs. Most patients had clinically silent tumors with no evidence of hormone excess and variable degrees of hypopituitarism; two had Cushing disease. All patients had macrotumors with a mean tumor size of 2.46 cm (range 1.1-5.0 cm). Crooke's hyaline change was identified in the nontumorous adenohypophysis of the two patients with Cushing disease. The mean Ki67 labeling index was 2.91% (range 2.03-3.94%). All tumors were negative for PIT1 and PIT1-lineage hormones (GH, PRL, and TSH). TPIT was focal in one tumor, and the remaining tumors had diffuse reactivity in more than 50% of tumor cells. SF1 expression was focal in 5 tumors and diffuse in one. Three tumors had variable expression of at least one gonadotropin (FSH or LH). GATA3 was expressed in two tumors. Variable ER-alpha expression was noted in three tumors. CAM5.2 was positive in all tumors. With the exception of two tumors causing Cushing disease, p27 expression was intact. Our study confirms that multilineage PitNETs expressing TPIT and SF1 occur but are extremely rare; they can be clinically non-functional or can cause Cushing disease. Irrespective of functional status of a PitNET, routine application of pituitary transcription factors is warranted to identify these tumors. Data on the molecular correlates and clinical significance are still needed for these rare multilineage PitNETs.

The gut microbiome in patients with Cushing's disease affects depression- and anxiety-like behavior in mice

BACKGROUND

Depression and anxiety significantly impact the quality of life in individuals with Cushing's disease (CD), which originates from pituitary neuroendocrine tumors (PitNETs), yet our understanding of the underlying mechanisms is limited. There is substantial evidence linking gut microbes to depression, anxiety, and endocrinology.

RESULTS

The gut bacterial phenotype of patients with Cushing's disease was significantly different from that of the control group, and when the mice were treated with fecal bacteria from these patients, both anxiety- and depression-like behavior were significantly increased. However, this effect can be alleviated by supplementing with 2-(14, 15-epoxyeicosatrienoyl) glycerol (2-14,15-EG) which was found at reduced levels in the peripheral blood of mice treated with coprofecal bacteria from Cushing's disease. In this process, the effects of hormone levels and immune factors were not significant. In addition, in an animal model, corticosterone has been observed to affect behavioral changes in mice through gut microbiota composition, clarifying the cause-and-effect relationship between hormones, microbiota, and behavior. Finally, there was no significant difference in gut microbiome composition and its effects on mouse behavior in patients with Cushing's disease with different levels of depression and anxiety.

CONCLUSIONS

In summary, this research enhances our current understanding of how gut microbes in patients with Cushing's disease contribute to depression and anxiety, offering novel insights for clinical treatment approaches. Video Abstract.

Molecular Basis of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (NETs) are rare well-differentiated neoplasms with limited therapeutic options and unknown cells of origin. The current classification of pancreatic neuroendocrine tumors is based on proliferative grading, and guides therapeutic strategies, however, tumors within grades exhibit profound heterogeneity in clinical manifestation and outcome. Manifold studies have highlighted intra-patient differences in tumors at the genetic and transcriptomic levels. Molecular classification might become an alternative or complementary basis for treatment decisions and reflect tumor biology, actionable cellular processes. Here, we provide a comprehensive review of genomic, transcriptomic, proteomic and epigenomic studies of pancreatic NETs to elucidate patterns shared between proposed subtypes that could form a foundation for new classification. We denote four NET subtypes with distinct molecular features, which were consistently reproduced using various omics technologies.

Analysis of the Status Quo and Influencing Factors of Revisiting Patients After Pituitary Tumor Resection: Based on a Chinese Patient Population

OBJECTIVE

To investigate the status of patients' post-pituitary tumor resection and analyze influencing factors, providing evidence for improved long-term management.

METHODS

The authors screened 1209 patients who underwent pituitary tumor resection at Zhejiang University's Second Affiliated Hospital from August 2020 to July 2022 using electronic medical records. Patients were classified into return visits (≥2 reviews/y or within 6 mo) and missing visit groups. Demographic and disease-related data were extracted from inpatient records, whereas return visits and prognosis data were collected from outpatient records and phone inquiries. Propensity score matching (1:1) was used to balance the groups, followed by univariate and multivariate logistic regression analyses to identify influencing factors.

RESULTS

Of the 1209 patients, 113 were unreachable. The study included 1095 patients, with 553 (50.5%) in the missing visit group and 542 (49.5%) in the return visit group. The authors matched 421 pairs, achieving balanced baseline data. Univariate analysis revealed significant differences in residence, unplanned readmission history, and current outcomes (P < 0.05). Multivariate analysis identified unplanned readmission history (odds ratio = 0.495, 95% CI: 0.307-0.799) as a protective factor. City residents had higher return visit rates than those from other provinces (odds ratio = 0.269, 95% CI: 0.610-1.579).

CONCLUSION

Postdischarge return rates for pituitary tumor resection patients are low and influenced by various factors. Improving return visit policies and systems is essential for facilitating outpatient follow-ups.

An Illustrated Review of the Recent 2019 World Health Organization Classification of Neuroendocrine Neoplasms: A Radiologic and Pathologic Correlation

ABSTRACT

Recent advances in molecular pathology and an improved understanding of the etiology of neuroendocrine neoplasms (NENs) have given rise to an updated World Health Organization classification. Since gastroenteropancreatic NENs (GEP-NENs) are the most common forms of NENs and their incidence has been increasing constantly, they will be the focus of our attention. Here, we review the findings at the foundation of the new classification system, discuss how it impacts imaging research and radiological practice, and illustrate typical and atypical imaging and pathological findings. Gastroenteropancreatic NENs have a highly variable clinical course, which existing classification schemes based on proliferation rate were unable to fully capture. While well- and poorly differentiated NENs both express neuroendocrine markers, they are fundamentally different diseases, which may show similar proliferation rates. Genetic alterations specific to well-differentiated neuroendocrine tumors graded 1 to 3 and poorly differentiated neuroendocrine cancers of small cell and large-cell subtype have been identified. The new tumor classification places new demands and creates opportunities for radiologists to continue providing the clinically most relevant report and on researchers to design projects, which continue to be clinically applicable.

Molecular Classification of Gastrointestinal and Pancreatic Neuroendocrine Neoplasms: Are We Ready for That?

In the last two decades, the increasing availability of technologies for molecular analyses has allowed an insight in the genomic alterations of neuroendocrine neoplasms (NEN) of the gastrointestinal tract and pancreas. This knowledge has confirmed, supported, and informed the pathological classification of NEN, clarifying the differences between neuroendocrine carcinomas (NEC) and neuroendocrine tumors (NET) and helping to define the G3 NET category. At the same time, the identification genomic alterations, in terms of gene mutation, structural abnormalities, and epigenetic changes differentially involved in the pathogenesis of NEC and NET has identified potential molecular targets for precision therapy. This review critically recapitulates the available molecular features of digestive NEC and NET, highlighting their correlates with pathological aspects and clinical characteristics of these neoplasms and revising their role as predictive biomarkers for targeted therapy. In this context, the feasibility and applicability of a molecular classification of gastrointestinal and pancreatic NEN will be explored.

The Clinicopathological Significance of Tumor Cell Subtyping in Appendiceal Neuroendocrine Tumors: A Series of 135 Tumors

Appendiceal neuroendocrine tumors (NETs) are common and often are identified as incidental lesions at the time of appendectomy. The guidelines for management are based on tumor size, degree of invasion, and the Ki67 proliferation index. Most small bowel NETs are composed of serotonin-producing EC-cells, but there are multiple other neuroendocrine cell types. In the rectum, there are L-cell tumors that express peptide YY (PYY), glucagon-like peptides (GLPs), and pancreatic polypeptide (PP); they are thought to have a better prognosis than serotonin-producing tumors. We investigated whether the appendix has distinct neuroendocrine tumor types based on cell type and whether that distinction has clinical significance. We collected 135 appendiceal NETs from the pathology archives of UHN Toronto and UHCMC (Cleveland). We analyzed the expression of biomarkers including CDX2, SATB2, PSAP, serotonin, glucagon (that detects GLPs), PYY, and pancreatic polypeptide (PP) and correlated the results with clinicopathologic parameters. Immunohistochemistry identified three types of appendiceal NETs. There were 75 (56%) classified as EC-cell tumors and 37 (27%) classified as L-cell tumors; the remaining 23 (17%) expressed serotonin and one of the L-cell biomarkers and were classified as mixed. EC-cell tumors were significantly larger with more extensive invasion involving the muscularis propria, subserosa, and mesoappendix compared with L-cell tumors. Mixed tumors were intermediate in all of these parameters. Both EC-cell and mixed tumors had lymphatic and/or vascular invasion while L-cell tumors had none. Unlike EC-cell NETs, L-cell tumors were not associated with lymph node metastasis. Tumor type correlated with pT stage and the only patient with distant metastatic disease in this series had an EC-cell tumor. Our study confirms that appendiceal NETs are not a homogeneous tumor population. There are at least three types of appendiceal NET, including EC-cell, L-cell, and mixed tumors. This information is important for surveillance of patients, as monitoring urinary 5HIAA levels is only appropriate for patients with serotonin-producing tumors, whereas measurement of GLPs and/or PP is more appropriate for patients with L-cell tumors. Our data also show that tumor type is of significance with EC-cell tumors exhibiting the most aggressive behavior.

Clinicopathological Analysis of Densely and Sparsely Granulated Somatotroph Tumors of Pituitary

OBJECTIVE

Somatotroph tumors are the second most common type of pituitary neuroendocrine tumors, which can be further classified into 2 subtypes-densely granulated somatotroph tumors (DGSTs) and sparsely granulated somatotroph tumors (SGSTs). The aim of this study was to investigate the clinical significance of the 2 subtypes in a retrospective analysis.

METHODS

From the database of the Ningbo Clinical Pathology Diagnosis Center, we collected patients diagnosed with pituitary somatotroph tumors. We then compiled pertinent clinical and radiological data and proceeded with histopathological examination involving hematoxylin-eosin staining and immunohistochemical staining. Subsequent analysis compared the 2 subtypes using either χ2 test or Fisher exact test.

RESULTS

We analyzed 40 cases of somatotroph tumors, 18 cases DGSTs and 22 SGSTs. Male-to-female ratio was 5:4 for DGSTs and 4:7 for SGSTs. Mean age was 52.83 years for DGSTs and 47.18 years for SGSTs. Statistically significant differences were observed between the DGST and SGST groups in invasiveness (P = 0.0267) and postoperative remission (P = 0.007). Cells of both DGSTs and SGSTs exhibited coexpression of PIT1, growth hormone, and CAM5.2, although the patterns of CAM5.2 expression differed between the 2 subtypes.

CONCLUSIONS

The efficacy of CAM5.2 staining in distinguishing between DGSTs and SGSTs was demonstrated. SGSTs, with their increased invasiveness and lower remission rate, are a high-risk subtype. The histological subtype of somatotroph tumors plays a crucial role in guiding treatment decisions and prognostic evaluation in affected patients.

Phenotype Transformation of PitNETs

Phenotype transformation in pituitary neuroendocrine tumors is a little-known and unpredictable clinical phenomenon. Previous studies have not clearly defined and systematically concluded on the causes of this rare phenomenon. Additionally, the mechanisms of phenotype transformation are not well known. We reviewed cases reported in the literature with the aim of defining phenotype transformation in pituitary neuroendocrine tumors. We present an overview of the wide spectrum of phenotype transformation and its clinical features. We also discuss findings on the potential mechanism of this rare transformation, which may be related to PC1/3, the bioactivity of secretory hormones, gene mutations and the plasticity of pituitary neuroendocrine tumors. Clinicians should be aware of this rare phenomenon and more studies on the underlying mechanisms are required.

Pathogenesis, clinical features, and treatment of plurihormonal pituitary adenoma

Plurihormonal pituitary adenoma (PPA) is a type of pituitary tumor capable of producing two or more hormones and usually presents as an aggressive, large adenoma. As yet, its pathogenesis remains unclear. This is the first study to systematically summarize the underlying pathogenesis of PPA. The pathogenesis is related to plurihormonal primordial stem cells, co-transcription factors, hormone co-expression, differential gene expression, and cell transdifferentiation. We conducted a literature review of PPA and analyzed its clinical characteristics. We found that the average age of patients with PPA was approximately 40 years, and most showed only one clinical symptom. The most common manifestation was acromegaly. Currently, PPA is treated with surgical resection. However, recent studies suggest that immunotherapy may be a potentially effective treatment.

Pathologic Characteristics of Somatotroph Pituitary Tumors-An Observational Single-Center Study

The pathologic evaluation of a tumor tissue is an essential part of an acromegaly patient's assessment. This study aimed to analyze the pathologic characteristics of pituitary tumors in patients with acromegaly. The demographic data, in addition to the hormonal, imaging, and pathologic results of 120 patients with acromegaly after pituitary surgery, were extracted from the Polish Acromegaly Registry. We compared sparsely and densely granulated tumors, GH(+), mixed GH(+)/PRL(+) and plurihormonal tumors, α-subunit-positive and α-subunit-negative tumors, and tumors of various Ki-67 indices in terms of the abovementioned features. Sparsely granulated tumors were more frequent in women than in men (p = 0.001) and in younger patients (p = 0.011), and they were larger (p < 0.001) compared to densely granulated tumors. Tumors with positive α-subunit were smaller (p = 0.013), showed extrasellar extension less often (p = 0.039), and were more often densely granulated (p < 0.001) compared to α-subunit-negative tumors. Patients with a higher Ki-67 index were younger (p < 0.001) and more often diagnosed with genetic syndromes (p = 0.02); they had higher GH concentrations (p = 0.007), larger tumors (p = 0.006), and cavernous sinus invasions more frequently (p = 0.022). Conclusions: The pathologic characteristics of somatotroph pituitary tumors are associated with patient's age, sex, hormonal results, tumor size, and the degree of extrasellar expansion.

Primary Pituitary Carcinoids Do Not Exist: A Reappraisal in the Era of Pituitary Neuroendocrine Tumours

The World Health Organization classification of pituitary tumours, published in 2022, supported a change in the terminology from "pituitary adenoma" to "pituitary neuroendocrine tumour" (PitNET). The neuroendocrine cells represent an integral part of the diffuse neuroendocrine system, including, among others, thyroid C cells, the parathyroid chief cells, and the anterior pituitary. Normal and neoplastic adenohypophyseal neuroendocrine cells have light microscopic, ultrastructural features and an immunoprofile compatible with the neuroendocrine cells and neuroendocrine tumours from other organs. Moreover, neuroendocrine cells of pituitary origin express transcription factors which indicate their cell-lineage origin. Thus, pituitary tumours are now considered as a continuum with other neuroendocrine tumours. PitNETs may occasionally be aggressive. In this context, the term "pituitary carcinoid" has no specific meaning: it either represents a PitNET, or a metastasis to the pituitary gland of a neuroendocrine tumour (NET). An accurate pathological evaluation, combined where necessary with functional radionuclide imaging, can define the origin of the tumour. We recommend that clinicians liaise with patient groups to understand the terminology to define primary tumours of adenohypophyseal cells. It is incumbent upon the responsible clinician to explain the use of the word "tumour" in a given clinical context.

The Unique Importance of Differentiation and Function in Endocrine Neoplasia

The assessment of cell differentiation in endocrine neoplasms involves not only the identification of a cell's structure and expression of specific transcription factors which regulate that cell, but also the identification of hormones and/or enzymes involved in hormone synthesis. The importance of this functional characterization is emphasized by the fact that the hormones serve as biomarkers for clinical surveillance to identify persistence, recurrence, or progression of disease. Sometimes, unusual patterns of hormone expression lead to unexpected clinical signs and symptoms. Loss of differentiated hormone production can be a sign of dedifferentiation as a tumor becomes more aggressive. In addition to prognostic information, cell differentiation can be predictive, since differentiated endocrine cells express targets for therapy, such as the sodium iodide symporter in thyroid cancers and somatostatin receptors in neuroendocrine tumors. The salient features of differentiation in the three main types of endocrine cells can be used to determine prognosis and to tailor management of patients with endocrine neoplasms.

The Spectrum of Endocrine Pathology

Endocrine pathology comprises a spectrum of disorders originating in various sites throughout the body. Some disorders affect endocrine glands, and others arise from endocrine cells that are dispersed in non-endocrine tissues. Endocrine cells can broadly be classified as neuroendocrine, steroidogenic, or thyroid follicular cells; these three families have distinct embryologic origins, morphologic structure, and biochemical hormone synthetic pathways. Lesions affecting the endocrine system include developmental abnormalities, inflammatory processes that can be infectious or autoimmune, hypofunction with atrophy or hyperfunction caused by hyperplasia secondary to pathology in other sites, and neoplasia of many types. Understanding endocrine pathology requires knowledge of both structure and function, including the biochemical signaling pathways that regulate hormone synthesis and secretion. Molecular genetics has clarified sporadic and hereditary disease that is common in this field.

[Unification of pathomorphological examination of patients with neuroendocrine tumors of the pituitary gland. Controversial issues of the new classification]

The progressive improvement of the classification using modern analytical methods is an essential tool for the development of precise and personalized approaches to the treatment of pituitary adenomas. In recent years, endocrinologists have witnessed evolutionary changes that have occurred in the histopathological identification of pituitary neoplasms, revealing new possibilities for studying tumorigenesis and predicting biological behavior.The paper considers the historical aspects of the gradual improvement of the classification of pituitary adenomas, as well as the new international 2022 WHO classification, according to which pituitary adenomas are included in the list of neuroendocrine tumors (PitNETs) to reflect the biological aggressiveness of some non-metastatic pituitary adenomas. The characteristics of pituitary adenoma are presented, as well as a list of histological subtypes of aggressive neuroendocrine tumors of the pituitary gland, marked by the main potentials for invasive growth, an increased risk of recurrence and a negative clinical prognosis.The expediency of changing the definition of «pituitary adenoma» to «neuroendocrine tumor» is discussed. It is emphasized that the introduction of a unified clinical, laboratory and morphological protocol into national clinical practice will help provide comparable comparative studies on the prognosis of the disease and the effectiveness of secondary therapy and also contribute to adequate management of potentially aggressive PitNETs.

PitNETs and the gut microbiota: potential connections, future directions

The role of the gut microbiome has been widely discussed in numerous works of literature. The biggest concern is the association of the gut microbiome with the central nervous system through the microbiome-brain-gut axis in the past ten years. As more and more research has been done on the relationship between the disease of the central nervous system and gut microbes. This fact is being revealed that gut microbes seem to play an important role from the onset and progression of the disease to clinical symptoms, and new treatments. As a special tumor of the central nervous system, pituitary neuroendocrine tumors (PitNETs)are closely related to metabolism, endocrinology, and immunity. These factors are the vectors through which intestinal microbes interact with the central nervous system. However, little is known about the effects of gut microbes on the PitNET. In this review, the relationship of gut microbiota in PitNETs is introduced, the potential effects of the gut-brain axis in this relationship are analyzed, and future research directions are presented.

Role of Tumor Microenvironment in Pituitary Neuroendocrine Tumors: New Approaches in Classification, Diagnosis and Therapy

Adenohypophysal pituitary tumors account for 10-15% of all intracranial tumors, and 25-55% display signs of invasiveness. Nevertheless, oncology still relies on histopathological examination to establish the diagnosis. Considering that the classification of pituitary tumors has changed significantly in recent years, we discuss the definition of aggressive and invasive tumors and the latest molecular criteria used for classifying these entities. The pituitary tumor microenvironment (TME) is essential for neoplastic development and progression. This review aims to reveal the impact of TME characteristics on stratifying these tumors in view of finding appropriate therapeutic approaches. The role of the pituitary tumor microenvironment and its main components, non-tumoral cells and soluble factors, has been addressed. The variable display of different immune cell types, tumor-associated fibroblasts, and folliculostellate cells is discussed in relation to tumor development and aggressiveness. The molecules secreted by both tumoral and non-tumoral cells, such as VEGF, FGF, EGF, IL6, TNFα, and immune checkpoint molecules, contribute to the crosstalk between the tumor and its microenvironment. They could be considered potential biomarkers for diagnosis and the invasiveness of these tumors, together with emerging non-coding RNA molecules. Therefore, assessing this complex network associated with pituitary neuroendocrine tumors could bring a new era in diagnosing and treating this pathology.

Clinical presentation and recurrence of pituitary neuroendocrine tumors: results from a single referral center in Colombia

INTRODUCTION

Pituitary neuroendocrine tumors (PitNETs) represent 15-18.2% of all intracranial tumors. Their clinical presentation can range from chronic headache, visual defects, hypopituitarism to hormone excess syndromes. PitNETS are commonly classified as functioning neuroendocrine tumors (F-PitNETs) and non-functioning neuroendocrine tumors (NF-PitNETs). At the moment, new classification has emerged based on cell lineages. Almost 50% of all patients with PitNETs require surgical intervention, and about 25% of these have residual and persistent disease that may require additional management.

SUBJECTS AND METHODS

A retrospective cohort of medical records of patients with PitNETs, aiming to describe the incidence of recurrence of patients who received surgical treatment over a 12 month follow up period at San Jose Hospital (SJH) in Bogotá, Colombia, over an observation period of 10 years. Furthermore, clinical presentation, biochemical characteristics and immunohistochemistry, postoperative complications are detailed.

RESULTS

Eight hundred and eighty-seven patients with pituitary tumors were included in the cohort; 83% (737/887) had a diagnosis of PitNET. Of these, 18.9% (140) received surgical management. The majority 58% (98/140) had nonfunctional-PitNETs (NF-PitNETs), followed by growth-hormone-secreting pituitary adenoma (22.1%; 33/140), adrenocorticotropic- hormone-secreting pituitary adenoma (9.3%; 13/140), and prolactinomas (9.3%; 13/140). A recurrence was found in 45.71% (64/140), subclassified as biochemical in 15.71% (22/140), controlled with medications in 20% (28/140), and remission occurred in 18.57% (26/140).

CONCLUSION

Clinical presentation and incidence of recurrence in patients with PitNETs in a referral center in Colombia are similar to other surgical cohorts with low cure rates and high recurrence.

Heterogeneity of TPIT expression in ACTH-secreting extra-pituitary neuroendocrine tumors (NETs) supports the existence of different cellular programs in pancreatic and pulmonary NETs

Extra-pituitary ACTH secretion is associated with a variety of neoplastic conditions and may cause the so-called ectopic ACTH-dependent Cushing syndrome (CS). The clarification of the mechanisms of extra-pituitary ACTH expression would provide potential therapeutic targets for this complex and severe disease. In the adenohypophysis, the transcription factor TPIT, co-operating with other molecules, induces POMC expression and ACTH production. However, no data are currently available on the presence and role of TPIT expression in extra-pituitary ACTH-producing neoplasms. This study was designed to explore TPIT expression in a series of pulmonary and pancreatic ACTH-producing tumors, either CS-associated or not. Forty-one extra-pituitary ACTH-producing neuroendocrine tumors (NETs) were included in the study, encompassing 32 NETs of the lung (LuNETs), 7 of the pancreas (PanNETs), and 2 pheochromocytomas. Of these, 9 LuNETs, all PanNETs, and the two pheochromocytomas were CS-associated. For comparison, 6 NETs of the pituitary gland (PitNETs; 3 ACTH-secreting and 3 ACTH-negative) and 35 ACTH-negative extra-pituitary NETs (15 Lu-NETs and 20 PanNETs) were analyzed. Immunohistochemistry with specific anti-TPIT antibodies and quantitative real-time PCR (qRT-PCR) were performed using standard protocols. TPIT expression was completely absent (protein and mRNA) in PanNETs, pheochromocytomas, and all ACTH-negative NETs. In contrast, it was expressed in 16/32 LuNETs, although with lower levels than in PitNETs. No definite relationship was found between immunohistochemistry TPIT expression and NET grade or the presence of Cushing syndrome. This study further highlights the clinical and biological heterogeneity of extra-pituitary ACTH secretion and suggests that the differences between ACTH-secreting PanNETs and LuNETs may mirror distinct molecular mechanisms underlying POMC expression. Our results point towards the recognition of a real corticotroph-like phenotype of ACTH-producing LuNETs, that is not a feature of ACTH-producing PanNETs.

From Emergence to Endemicity: A Comprehensive Review of COVID-19

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), later renamed coronavirus disease 2019 (COVID-19), was first identified in Wuhan, China, in early December 2019. Initially, the China office of the World Health Organization was informed of numerous cases of pneumonia of unidentified etiology in Wuhan, Hubei Province at the end of 2019. This would subsequently result in a global pandemic with millions of confirmed cases of COVID-19 and millions of deaths reported to the WHO. We have analyzed most of the data published since the beginning of the pandemic to compile this comprehensive review of SARS-CoV-2. We looked at the core ideas, such as the etiology, epidemiology, pathogenesis, clinical symptoms, diagnostics, histopathologic findings, consequences, therapies, and vaccines. We have also included the long-term effects and myths associated with some therapeutics of COVID-19. This study presents a comprehensive assessment of the SARS-CoV-2 virology, vaccines, medicines, and significant variants identified during the course of the pandemic. Our review article is intended to provide medical practitioners with a better understanding of the fundamental sciences, clinical treatment, and prevention of COVID-19. As of May 2023, this paper contains the most recent data made accessible.

Three Dimensional Models of Endocrine Organs and Target Tissues Regulated by the Endocrine System

Immortalized cell lines originating from tumors and cultured in monolayers in vitro display consistent behavior and response, and generate reproducible results across laboratories. However, for certain endpoints, these cell lines behave quite differently from the original solid tumors. Thereby, the homogeneity of immortalized cell lines and two-dimensionality of monolayer cultures deters from the development of new therapies and translatability of results to the more complex situation in vivo. Organoids originating from tissue biopsies and spheroids from cell lines mimic the heterogeneous and multidimensional characteristics of tumor cells in 3D structures in vitro. Thus, they have the advantage of recapitulating the more complex tissue architecture of solid tumors. In this review, we discuss recent efforts in basic and preclinical cancer research to establish methods to generate organoids/spheroids and living biobanks from endocrine tissues and target organs under endocrine control while striving to achieve solutions in personalized medicine.

PD-L1 Expression in Pituitary Neuroendocrine Tumors/Pituitary Adenomas

BACKGROUND AND AIM

About a third of Pituitary Neuroendocrine Tumors (PitNETs) may show aggressive behavior. Many efforts have been performed for identifying possible predictive factors to early determine the future behavior of PitNETs. Programmed cell death ligand 1 (PD-L1) expression was associated with a more aggressive biology in different solid tumors, but its role in PitNET is not well-established yet. Our study aims to analyze PD-L1 expression in a surgical cohort of PitNETs to determine its association with radiological invasion and pathology findings, as well as with long-term recurrence rates.

METHODS

We performed a retrospective analysis in a series of 86 PitNETs. Clinical presentation and radiological features of the preoperative period were collected, as well as pathological data and follow-up data. The rate of PD-L1 expression was immunohistochemically evaluated and expressed as a tumor proportion score (TPS). We assessed its relationship with cavernous sinus invasion and Trouillas' classification as primary outcomes. Secondary outcomes included the TPS' relationship with histopathological markers of proliferation, hormonal expression, tumor size and long-term recurrence rates. We calculated the optimal cut-point for the primary outcomes while maximizing the product of the sensitivity and specificity and then we evaluated the significance of secondary outcomes with logistic regression analysis.

RESULTS

Eighty-six patients were included in the analysis; 50 cases were non-functional PitNETs. The TPS for PD-L1 showed a highly right-skewed distribution in our sample, as 30.2% of patients scored 0. Using Trouillas' classification, we found that "proliferative" cases have a significantly higher probability to express PD-L1 in more than 30% of tumor cells (OR: 5.78; CI 95%: 1.80-18.4). This same cut-point was also associated with p53 expression. A positive association was found between PD-L1 expression and GH expression (p = 0.001; OR: 5.44; CI 95%: 1.98-14.98), while an inverse relationship was found with FSH/LH expression (p = 0.014; OR = 0.27, CI 95%: 0.10-0.76). No association was found with CS invasion, tumor size, bone erosion or dura invasion. We could not find any association between PD-L1 expression and recurrence.

CONCLUSIONS

PD-L1 expression was associated with proliferative grades of Trouillas' classification and p53 expression. We also confirmed a higher expression of PD-L1 in somatotroph tumors. Larger studies are necessary to investigate the relationship between PD-L1 expression and aggressive behaviors.

Pathology of Crooke Cells in the Human Pituitaries: A Timely Review

Crooke cell change was first found in the regressed and suppressed corticotroph (adrenocorticotropic hormone-producing) cells, and now is known to occur in pituitary tumors. The tumor cells of this type can be recognized by morphology with immunohistochemistry, and are well known to predict aggressive behavior such as invasion and rare metastases. This is one of the representative neuroendocrine tumors in the pituitary which is now considered to have malignant potential as proposed in the pancreas and gastrointestinal tracts. It is important to emphasize the pituitary tumor pathology such as Crooke cell change for prognostication and appropriate therapies. This review article describes the evolution from the Crooke cells to Crooke cell tumors which is timely along with the Fifth WHO classification 2022 published online.

The Role of Activation of PI3K/AKT/mTOR and RAF/MEK/ERK Pathways in Aggressive Pituitary Adenomas-New Potential Therapeutic Approach-A Systematic Review

Pituitary tumors (PT) are mostly benign, although occasionally they demonstrate aggressive behavior, invasion of surrounding tissues, rapid growth, resistance to conventional treatments, and multiple recurrences. The pathogenesis of PT is still not fully understood, and the factors responsible for its invasiveness, aggressiveness, and potential for metastasis are unknown. RAF/MEK/ERK and mTOR signaling are significant pathways in the regulation of cell growth, proliferation, and survival, its importance in tumorigenesis has been highlighted. The aim of our review is to determine the role of the activation of PI3K/AKT/mTOR and RAF/MEK/ERK pathways in the pathogenesis of pituitary tumors. Additionally, we evaluate their potential in a new therapeutic approach to provide alternative therapies and improved outcomes for patients with aggressive pituitary tumors that do not respond to standard treatment. We perform a systematic literature search using the PubMed, Embase, and Scopus databases (search date was 2012-2023). Out of the 529 screened studies, 13 met the inclusion criteria, 7 related to the PI3K/AKT/mTOR pathway, and 7 to the RAF/MEK/ERK pathway (one study was used in both analyses). Understanding the specific factors involved in PT tumorigenesis provides opportunities for targeted therapies. We also review the possible new targeted therapies and the use of mTOR inhibitors and TKI in PT management. Although the RAF/MEK/ERK and PI3K/AKT/mTOR pathways play a pivotal role in the complex signaling network along with many interactions, further research is urgently needed to clarify the exact functions and the underlying mechanisms of these signaling pathways in the pathogenesis of pituitary adenomas and their role in its invasiveness and aggressive clinical outcome.

Cauda Equina Neuroendocrine Tumors: Distinct Epithelial Neuroendocrine Neoplasms of Spinal Origin

The tumor formerly known as "cauda equina paraganglioma" was recently renamed as cauda equina neuroendocrine tumor (CENET) based on distinct biological and genetic properties. Nevertheless, it remains insufficiently understood. For this study, we retrieved CENETs (some previously reported), from the pathology files of 3 institutions; we examined their immunohistochemical profile, including common neuroendocrine tumor-associated hormones and transcription factors. We identified 24 CENETs from 7 female and 17 male adult patients, with a median age of 47 years. Six included neurofilament-positive ganglion cells. All tumors tested were positive for INSM1, synaptophysin, chromogranin A, SSTR2, and CD56 as well as at least 1 keratin (AE1/AE3, CAM5.2); CK7 and CK20 were negative. Glial fibrillary acidic protein was negative, except for peripheral nontumoral elements. S100 protein was variable but mainly expressed in scattered sustentacular cells. All but 1 tumor tested were positive for HOXB13; several stained for SATB2, and all tumors were consistently negative for GATA3. All tumors tested were negative for transcription factors found in various other epithelial neuroendocrine neoplasms including TTF1, CDX2, PIT1, TPIT, SF1, and PAX8; staining for T-brachyury was negative. Four of 5 CENETs tested had at least focal tyrosine hydroxylase reactivity. Serotonin expression was detected in all 21 tumors tested; it was diffusely positive in 5 and had variable positivity in the remainder. A few tumors had scattered cells expressing gastrin, calcitonin, pancreatic polypeptide, and peptide YY, while glucagon, adrenocorticotropic hormone, and monoclonal carcinoembryonic antigen were negative. PSAP expression was found focally in 4 of 5 tumors examined. SDHB was consistently intact; ATRX was intact in 14 tumors and showed only focal loss in 3. The median Ki-67 labeling index was 4.5% (range: 1% to 15%). We conclude that CENET represents a distinct neuroendocrine neoplasm; the subset with ganglion cells qualifies for designation as composite gangliocytoma/neuroma-neuroendocrine tumor (CoGNET) as defined in the 2022 WHO classification of neuroendocrine neoplasms. In addition to INSM1, chromogranin, synaptophysin, and keratins, the most characteristic finding is nuclear HOXB13 expression; a subset also express SATB2. Serotonin is the most common hormone expressed. The cytogenesis and pathogenesis of these lesions remains unclear.

Aggressive pituitary tumors (PitNETs)

The majority of anterior pituitary tumors behave benignly, that is, they grow slowly and do not metastasize, and were therefore called adenomas. However, they would frequently invade adjacent structures, leading to recurrence. One of the misleading assumptions in their previous classification was the simplistic distinction made between adenoma and carcinoma. In the upcoming WHO 2022 classification, a new terminology will be introduced: pituitary neuroendocrine tumor (PitNET) which is consistent with that used for other neuroendocrine neoplasms. In general, aggressive PitNETs are invasive and proliferative tumors with frequent recurrences, resistant to conventional treatments, and yet virtually without metastases. At present, no single morphological or histological marker has been shown as yet to reliably predict their aggressive behavior. In terms of treatment, temozolomide (TMZ) had been considered promising and the sole therapeutic option for aggressive and malignant PitNETs following failure of standard therapies. However, recent reports have disclosed that TMZ does not provide long-term control of many aggressive PitNETs. A further multidisciplinary approach is necessary for both reliable prediction and successful management of aggressive PitNETs.

The Spectrum of Familial Pituitary Neuroendocrine Tumors

Hereditary pituitary tumorigenesis is seen in a relatively small proportion (around 5%) of patients with pituitary neuroendocrine tumors (PitNETs). The aim of the current review is to describe the main clinical and molecular features of such pituitary tumors associated with hereditary or familial characteristics, many of which have now been genetically identified. The genetic patterns of inheritance are classified into isolated familial PitNETs and the syndromic tumors. In general, the established genetic causes of familial tumorigenesis tend to present at a younger age, often pursue a more aggressive course, and are more frequently associated with growth hormone hypersecretion compared to sporadic tumors. The mostly studied molecular pathways implicated are the protein kinase A and phosphatidyl-inositol pathways, which are in the main related to mutations in the syndromes of familial isolated pituitary adenoma (FIPA), Carney complex syndrome, and X-linked acrogigantism. Another well-documented mechanism consists of the regulation of p27 or p21 proteins, with further acceleration of the pituitary cell cycle through the check points G1/S and M/G1, mostly documented in multiple endocrine neoplasia type 4. In conclusion, PitNETs may occur in relation to well-established familial germline mutations which may determine the clinical phenotype and the response to treatment, and may require family screening.

Diagnostic, Prognostic, and Predictive Role of Ki67 Proliferative Index in Neuroendocrine and Endocrine Neoplasms: Past, Present, and Future

The introduction of Ki67 immunohistochemistry in the work-up of neuroendocrine neoplasms (NENs) has opened a new approach for their diagnosis and prognostic evaluation. Since the first demonstration of the prognostic role of Ki67 proliferative index in pancreatic NENs in 1996, several studies have been performed to explore its prognostic, diagnostic, and predictive role in other neuroendocrine and endocrine neoplasms. A large amount of information is now available and published results globally indicate that Ki67 proliferative index is useful to this scope, although some differences exist in relation to tumor site and type. In gut and pancreatic NENs, the Ki67 proliferative index has a well-documented and accepted diagnostic and prognostic role and its evaluation is mandatory in their diagnostic work-up. In the lung, the Ki67 index is recommended for the diagnosis of NENs on biopsy specimens, but its diagnostic role in surgical specimens still remains to be officially accepted, although its prognostic role is now well documented. In other organs, such as the pituitary, parathyroid, thyroid (follicular cell-derived neoplasms), and adrenal medulla, the Ki67 index does not play a diagnostic role and its prognostic value still remains a controversial issue. In medullary thyroid carcinoma, the Ki67 labelling index is used to define the tumor grade together with other morphological parameters, while in the adrenal cortical carcinoma, it is useful to select patients to treated with mitotane therapy. In the present review, the most important information on the diagnostic, prognostic, and predictive role of Ki67 proliferative index is presented discussing the current knowledge. In addition, technical issues related to the evaluation of Ki67 proliferative index and the future perspectives of the application of Ki67 immunostaining in endocrine and neuroendocrine neoplasms is discussed.

Imaging of pituitary tumors: an update with the 5th WHO Classifications-part 1. Pituitary neuroendocrine tumor (PitNET)/pituitary adenoma

The pituitary gland is the body's master gland of the endocrine glands. Although it is a small organ, many types of tumors can develop within it. The recently revised fifth edition of the World Health Organization (WHO) classifications (2021 World Health Organization Classification of Central Nervous System Tumors and 2022 World Health Organization Classification of Endocrine and Neuroendocrine Tumors) revealed significant changes to the classification of pituitary adenomas, the most common type of pituitary gland tumor. This change categorized pituitary adenomas as neuroendocrine tumors and proposed the name to be revised to pituitary neuroendocrine tumor (PitNET). The International Classification of Diseases for Oncology behavior code for this tumor was previously "0" for benign tumor. In contrast, the fifth edition WHO classification has changed this code to "3" for primary malignant tumors as same to neuroendocrine tumor in other organs. Because the WHO classification made an important and significant change in the fundamental concept of the disease, in this paper, we will discuss the imaging diagnosis (magnetic resonance imaging, computed tomography, and positron emission tomography) of PitNET/pituitary adenoma in detail, considering these revisions as per the latest version of the WHO classification.

Post-operative surveillance for somatotroph, lactotroph and non-functional pituitary adenomas after curative resection: a systematic review

CONTEXT

Pituitary tumors are the third most common brain tumor and yet there is no standardization of the surveillance schedule and assessment modalities after transsphenoidal surgery.

EVIDENCE ACQUISITION

OVID, EMBASE and the Cochrane Library databases were systematically screened from database inception to March 5, 2020. Inclusion and exclusion criteria were designed to capture studies examining detection of pituitary adenoma recurrence in patients 18 years of age and older following surgical resection with curative intent.

EVIDENCE SYNTHESIS

A total of 7936 abstracts were screened, with 812 articles reviewed in full text and 77 meeting inclusion criteria for data extraction. A pooled analysis demonstrated recurrence rates at 1 year, 5 years and 10 years for non-functioning pituitary adenomas (NFPA; N = 3533 participants) were 1%, 17%, and 33%, for prolactin-secreting adenomas (PSPA; N = 1295) were 6%, 21%, and 28%, and for growth-hormone pituitary adenomas (GHPA; N = 1257) were 3%, 8% and 13%, respectively. Rates of recurrence prior to 1 year were 0% for NFPA, 1-2% for PSPA and 0% for GHPA. The mean time to disease recurrence for NFPA, PSPA and GHPA were 4.25, 2.52 and 4.18 years, respectively.

CONCLUSIONS

This comprehensive review of the literature quantified the recurrence rates for commonly observed pituitary adenomas after transsphenoidal surgical resection with curative intent. Our findings suggest that surveillance within 1 year may be of low yield. Further clinical trials and cohort studies investigating cost-effectiveness of surveillance schedules and impact on quality of life of patients under surveillance will provide further insight to optimize follow-up.

The Complex Histopathological and Immunohistochemical Spectrum of Neuroendocrine Tumors-An Overview of the Latest Classifications

Neuroendocrine neoplasms (NENs) originate from the neuroendocrine cell system, which may either take the shape of organoid cell aggregations or be composed of dispersed cells across various organs. Therefore, these tumors are heterogenous regarding the site of origin, functional status, degree of aggressiveness, and prognosis. When treating patients with neuroendocrine tumors, one of the most significant challenges for physicians is determining the correct tumor grade and thus classifying patients into risk categories. Over the years, the classification of these tumors has changed significantly, often causing confusion due to clinical, molecular, and immunohistochemical variability. This review aims to outline the latest NENs classifications regardless of their site of origin. Thus, an overview of the key histopathological and immunohistochemical characteristics of NENs could pave the way to validate possible predictive and prognostic markers and also guide the therapeutic conduct.

An Overview of Pituitary Neuroendocrine Tumors (PitNET) and Algorithmic Approach to Diagnosis

The diagnostic algorithm and nomenclature of pituitary neuroendocrine tumors have evolved over the past decade, beginning with simpler categorical schemes focused on histomorphologic features and moving to a more sophisticated lineage-specific categorization. This contemporary overview highlights a multimodal approach to pituitary neuroendocrine tumors with a focus on changes in nomenclature, classification, and subclassification; including, brief comments on treatment, and new guidelines for genetic screening, particularly for young patients with such neoplasms.

Moving toward a standardized diagnostic statement of pituitary adenoma using an information extraction model: a real-world study based on electronic medical records

PURPOSE

Diagnostic statements for pituitary adenomas (PAs) are complex and unstandardized. We aimed to determine the most commonly used elements contained in the statements and their combination patterns and variations in real-world clinical practice, with the ultimate goal of promoting standardized diagnostic recording and establishing an efficient element extraction process.

METHODS

Patient medical records from 2012 to 2020 that included PA among the first three diagnoses were included. After manually labeling the elements in the diagnostic texts, we obtained element types and training sets, according to which an information extraction model was constructed based on the word segmentation model "Jieba" to extract information contained in the remaining diagnostic texts.

RESULTS

A total of 576 different diagnostic statements from 4010 texts of 3770 medical records were enrolled in the analysis. The first ten diagnostic elements related to PA were histopathology, tumor location, endocrine status, tumor size, invasiveness, recurrence, diagnostic confirmation, Knosp grade, residual tumor, and refractoriness. The automated extraction model achieved F1-scores that reached 100% for all ten elements in the second round and 97.3-100.0% in the test set consisting of an additional 532 diagnostic texts. Tumor location, endocrine status, histopathology, and tumor size were the most commonly used elements, and diagnoses composed of the above elements were the most frequent. Endocrine status had the greatest expression variability, followed by Knosp grade. Among all the terms, the percentage of loss of tumor size was among the highest (21%). Among statements where the principal diagnoses were PAs, 18.6% did not have information on tumor size, while for those with other diagnoses, this percentage rose to 48% (P < 0.001).

CONCLUSION

Standardization of the diagnostic statement for PAs is unsatisfactory in real-world clinical practice. This study could help standardize a structured pattern for PA diagnosis and establish a foundation for research-friendly, high-quality clinical information extraction.

Multiple tumorous lesions of the pituitary gland

PURPOSE/OBJECTIVE

Multiple tumorous lesions in one pituitary gland are rare and mostly described in case reports. Their incidences and combinations are defined in larger collectives. Therefore, we analyzed our large collection for double tumors and combinations of tumors, cysts, and inflammation.

METHODS

The German Registry of Pituitary Tumors, including cases from 1990 to 2018, served as the database. Our collection comprises a total of 16,283 cases up until the end of 2018. Of these cases, 12,673 originated from surgical and 3,610 from autopsy material. All specimens were fixed in formalin and embedded in paraffin. The sections were stained with hematoxylin-eosin and PAS. Monoclonal (prolactin, TSH, FSH, LH, and α subunit) or polyclonal (GH and ACTH) antibodies were used to detect pituitary hormones in the lesions. Since 2017, antibodies against the transcription factors Pit-1, T-Pit, and SF-1 have been used in difficult cases. The criteria of the 2017 WHO classification have been basic principles for classification since 2018 (Osamura et al. 2017). For differentiation of other sellar tumors, such as meningiomas, chordomas, or metastases, the use of additional antibodies was necessary. For these cases, it was possible to use a broad antibody spectrum. Autopsy pituitaries were generally studied by H&E and PAS sections. If any lesions were demonstrated in these specimens, additional immunostaining was performed.

RESULTS

Multiple tumorous lesions with more than one pituitary neuroendocrine tumor (PitNET) respectively adenoma make up 1.4% (232 cases) in our collection. Within the selected cases, synchronous multiple pituitary neuroendocrine tumors (PitNETs) account for 17.3%, PANCH cases (pituitary adenoma with neuronal choristoma) for 14.7%, PitNETs and posterior lobe tumors for 2.2%, PitNETs and metastases for 5.2%, PitNETs and mesenchymal tumors for 2.6%, PitNETs and cysts for 52.2%, and PitNETs and primary inflammation for 6.0%. The mean patient age was 53.8 years, with a standard deviation of 18.5 years. A total of 55.3% of the patients were female and 44.7% were male. From 1990 to 2018, there was a continuous increase in the number of multiple tumorous lesions.

CONCLUSION

From our studies, we conclude that considering possible tumorous double lesions during surgeries and in preoperative X-ray analyses is recommended.

Overview of the 2022 WHO Classification of Pituitary Adenomas/Pituitary Neuroendocrine Tumors: Clinical Practices, Controversies, and Perspectives

The latest edition of the WHO classification of the central nervous system was published in 2021. This review summarizes the major revisions to the classification of anterior pituitary tumors. The most important revision involves preferring the terminology of pituitary neuroendocrine tumor (PitNET), even though the terminology of pituitary adenoma (PA) still can be used according to this WHO classification compared to the previous one. Moreover, immunohistochemistry (IHC) examination of pituitary-specific transcription factors (TFs), including PIT1, TPIT, SF-1, GATA2/3, and ERα, is endorsed to determine the tumor cell lineage and to facilitate the classification of PitNET/PA subgroups. However, TF-negative IHC staining indicates PitNET/PA with no distinct cell lineages, which includes unclassified plurihormonal (PH) tumors and null cell (NC) tumors in this edition. The new WHO classification of PitNET/PA has incorporated tremendous advances in the understanding of the cytogenesis and pathogenesis of pituitary tumors. However, due to the shortcomings of the technology used in the diagnosis of PitNET/PA and the limited understanding of the tumorigenesis of PitNET/PA, the application of this new classification system in practice should be further evaluated and validated. Besides providing information for deciding the follow-up plans and adjunctive treatment after surgery, this classification system offers no additional help for neurosurgeons in clinical practice, especially in determining the treatment strategies. Therefore, it is necessary for neurosurgeons to establish a comprehensive pituitary classification system for PitNET/PA that incorporates neuroimaging grading data or direct observation of invasiveness during operation or the predictor of prognosis, as well as pathological diagnosis, thereby distinguishing the invasiveness of the tumor and facilitating neurosurgeons to decide on the treatment strategies and follow-up plans as well as adjunctive treatment after surgery.

Two Pituitary Neuroendocrine Tumors (PitNETs) with Very High Proliferation and TP53 Mutation - High-Grade PitNET or PitNEC?

We report two pituitary neuroendocrine tumors (PitNETs) with very high Ki67 labeling indices, many mitoses and TP53 mutation (nearly all tumor cell nuclei were positive for p53). One of the tumors had bone and liver metastases. One was a corticotroph cell tumor; the other was a lactotroph tumor. The classification of these tumors is the subject of this discussion. Traditionally, pituitary carcinomas are only diagnosed by demonstration of metastases according to the 2017 WHO classification. In contrast, neuroendocrine neoplasms of the gastrointestinal tract and pancreas are classified as either well differentiated NETs that are graded as G1, G2, and G3 based on proliferation as determined by Ki67 indices of ≤ 3, 3-20 and > 20%, and/or < 2, 2-20, and > 20 mitoses per 10 high-power field respectively, or as neuroendocrine carcinomas (NECs) that are poorly differentiated neoplasms with mitoses > 20/HPF and/or a Ki67 index > 20%. With the reclassificiation of PitNETs, in our opinion, the adequate term for the well-differentiated corticotroph tumor that we report is a PitNET G3, whereas the undifferentiated prolactin tumor should be classified as PitNEC. This report expands the spectrum of pituitary neuroendocrine neoplasms.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Overview of the 2022 WHO Classification of Head and Neck Neuroendocrine Neoplasms

This review article provides a brief overview of the new WHO classification by adopting a question-answer model to highlight the spectrum of head and neck neuroendocrine neoplasms which includes epithelial neuroendocrine neoplasms (neuroendocrine tumors and neuroendocrine carcinomas) arising from upper aerodigestive tract and salivary glands, and special neuroendocrine neoplasms including middle ear neuroendocrine tumors (MeNET), ectopic or invasive pituitary neuroendocrine tumors (PitNET; formerly known as pituitary adenoma) and Merkel cell carcinoma as well as non-epithelial neuroendocrine neoplasms (paragangliomas). The new WHO classification follows the IARC/WHO nomenclature framework and restricts the diagnostic term of neuroendocrine carcinoma to poorly differentiated epithelial neuroendocrine neoplasms. In this classification, well-differentiated epithelial neuroendocrine neoplasms are termed as neuroendocrine tumors (NET), and are graded as G1 NET (no necrosis and < 2 mitoses per 2 mm²; Ki67 < 20%), G2 NET (necrosis or 2-10 mitoses per 2 mm², and Ki67 < 20%) and G3 NET (> 10 mitoses per 2 mm² or Ki67 > 20%, and absence of poorly differentiated cytomorphology). Neuroendocrine carcinomas (> 10 mitoses per 2 mm², Ki67 > 20%, and often associated with a Ki67 > 55%) are further subtyped based on cytomorphological characteristics as small cell and large cell neuroendocrine carcinomas. Unlike neuroendocrine carcinomas, head and neck NETs typically show no aberrant p53 expression or loss of RB reactivity. Ectopic or invasive PitNETs are subtyped using pituitary transcription factors (PIT1, TPIT, SF1, GATA3, ER-alpha), hormones and keratins (e.g., CAM5.2). The new classification emphasizes a strict correlation of morphology and immunohistochemical findings in the accurate diagnosis of neuroendocrine neoplasms. A particular emphasis on the role of biomarkers in the confirmation of the neuroendocrine nature of a neoplasm and in the distinction of various neuroendocrine neoplasms is provided by reviewing ancillary tools that are available to pathologists in the diagnostic workup of head and neck neuroendocrine neoplasms. Furthermore, the role of molecular immunohistochemistry in the diagnostic workup of head and neck paragangliomas is discussed. The unmet needs in the field of head and neck neuroendocrine neoplasms are also discussed in this article. The new WHO classification is an important step forward to ensure accurate diagnosis that will also form the basis of ongoing research in this field.

Overview of the 2022 WHO Classification of Neuroendocrine Neoplasms

In this review, we detail the changes and the relevant features that are applied to neuroendocrine neoplasms (NENs) in the 2022 WHO Classification of Endocrine and Neuroendocrine Tumors. Using a question-and-answer approach, we discuss the consolidation of the nomenclature that distinguishes neuronal paragangliomas from epithelial neoplasms, which are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The criteria for these distinctions based on differentiation are outlined. NETs are generally (but not always) graded as G1, G2, and G3 based on proliferation, whereas NECs are by definition high grade; the importance of Ki67 as a tool for classification and grading is emphasized. The clinical relevance of proper classification is explained, and the importance of hormonal function is examined, including eutopic and ectopic hormone production. The tools available to pathologists for accurate classification include the conventional biomarkers of neuroendocrine lineage and differentiation, INSM1, synaptophysin, chromogranins, and somatostatin receptors (SSTRs), but also include transcription factors that can identify the site of origin of a metastatic lesion of unknown primary site, as well as hormones, enzymes, and keratins that play a role in functional and structural correlation. The recognition of highly proliferative, well-differentiated NETs has resulted in the need for biomarkers that can distinguish these G3 NETs from NECs, including stains to determine expression of SSTRs and those that can indicate the unique molecular pathogenetic alterations that underlie the distinction, for example, global loss of RB and aberrant p53 in pancreatic NECs compared with loss of ATRX, DAXX, and menin in pancreatic NETs. Other differential diagnoses are discussed with recommendations for biomarkers that can assist in correct classification, including the distinctions between epithelial and non-epithelial NENs that have allowed reclassification of epithelial NETs in the spine, in the duodenum, and in the middle ear; the first two may be composite tumors with neuronal and glial elements, and as this feature is integral to the duodenal lesion, it is now classified as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). The many other aspects of differential diagnosis are detailed with recommendations for biomarkers that can distinguish NENs from non-neuroendocrine lesions that can mimic their morphology. The concepts of mixed neuroendocrine and non-neuroendocrine (MiNEN) and amphicrine tumors are clarified with information about how to approach such lesions in routine practice. Theranostic biomarkers that assist patient management are reviewed. Given the significant proportion of NENs that are associated with germline mutations that predispose to this disease, we explain the role of the pathologist in identifying precursor lesions and applying molecular immunohistochemistry to guide genetic testing.

Overview of the 2022 WHO Classification of Pituitary Tumors

This review summarizes the changes in the 5th Edition of the WHO Classification of Endocrine and Neuroendocrine Tumors that relate to the pituitary gland. The new classification clearly distinguishes anterior lobe (adenohypophyseal) from posterior lobe (neurohypophyseal) and hypothalamic tumors. Other tumors arising in the sellar region are also discussed. Anterior lobe tumors include (i) well-differentiated adenohypophyseal tumors that are now classified as pituitary neuroendocrine tumors (PitNETs; formerly known as pituitary adenomas), (ii) pituitary blastoma, and (iii) the two types of craniopharyngioma. The new WHO classification provides detailed histological subtyping of a PitNET based on the tumor cell lineage, cell type, and related characteristics. The routine use of immunohistochemistry for pituitary transcription factors (PIT1, TPIT, SF1, GATA3, and ERα) is endorsed in this classification. The major PIT1, TPIT, and SF1 lineage-defined PitNET types and subtypes feature distinct morphologic, molecular, and clinical differences. The "null cell" tumor, which is a diagnosis of exclusion, is reserved for PitNETs with no evidence of adenohypophyseal lineage differentiation. Unlike the 2017 WHO classification, mammosomatotroph and acidophil stem cell tumors represent distinct PIT1-lineage PitNETs. The diagnostic category of PIT1-positive plurihormonal tumor that was introduced in the 2017 WHO classification is replaced by two clinicopathologically distinct PitNETs: the immature PIT1-lineage tumor (formerly known as silent subtype 3 tumor) and the mature plurihormonal PIT1-lineage tumor. Rare unusual plurihormonal tumors feature multi-lineage differentiation. The importance of recognizing multiple synchronous PitNETs is emphasized to avoid misclassification. The term "metastatic PitNET" is advocated to replace the previous terminology "pituitary carcinoma" in order to avoid confusion with neuroendocrine carcinoma (a poorly differentiated epithelial neuroendocrine neoplasm). Subtypes of PitNETs that are associated with a high risk of adverse biology are emphasized within their cell lineage and cell type as well as based on clinical variables. Posterior lobe tumors, the family of pituicyte tumors, include the traditional pituicytoma, the oncocytic form (spindle cell oncocytoma), the granular cell form (granular cell tumor), and the ependymal type (sellar ependymoma). Although these historical terms are entrenched in the literature, they are nonspecific and confusing, such that oncocytic pituicytoma, granular cell pituicytoma, and ependymal pituicytoma are now proposed as more accurate. Tumors with hypothalamic neuronal differentiation are classified as gangliocytomas or neurocytomas based on large and small cell size, respectively. This classification sets the standard for a high degree of sophistication to allow individualized patient management approaches.

Pituitary carcinoma: reclassification and implications in the NET schema

The entity known as pituitary carcinoma has been traditionally defined as a tumor of adenohypophysial cells that metastasizes systemically or craniospinally independent of the histological appearance of the lesion. Reported cases of pituitary carcinoma have clinically and histologically resembled their non-metastatic counterparts that were classified as adenomas; the majority of cases were initially diagnosed as adenomas, and with tumor progression and spread, the diagnosis was changed to carcinoma. This classification has been challenged since the definition of malignancy in most organs is not based only on metastatic spread. The extent of local invasion resulting in an inability to completely resect an adenohypophysial tumor can have serious consequences that can cause harm and are therefore not benign. To address this dilemma, it was proposed that pituitary tumors be classified as neuroendocrine tumors. This change in nomenclature is totally appropriate since these tumors are composed of classical neuroendocrine cells; as with other neuroendocrine tumors, they have variable behavior that can be indolent but can involve metastasis. With the new nomenclature, there is no requirement for a distinction between adenomas and carcinomas. Moreover, the WHO/IARC has provided an overarching classification for neuroendocrine neoplasms at all body sites; in this new classification, the term 'neuroendocrine carcinoma' is reserved for poorly differentiated high-grade malignancies that are clinically, morphologically and genetically distinct from well-differentiated neuroendocrine tumors. It remains to be determined if there are true pituitary neuroendocrine carcinomas.