Colorectal mixed adenoneuroendocrine carcinomas and neuroendocrine carcinomas are genetically closely related to colorectal adenocarcinomas

Mixed neuroendocrine-non-neuroendocrine neoplasm of the colon treated with laparoscopic resection and adjuvant chemotherapy: a case report

Mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) of the colon is rare with a poor prognosis. Since the first description of a mixed neoplasm 100 years ago, the nomenclature has evolved, most recently with the 2022 World Health Organization (WHO) classification system. We describe our experience of a case of locoregionally advanced MiNEN of the descending colon treated with curative laparoscopic resection and adjuvant chemotherapy. The patient is a 72 year old woman who presented with haematochezia. Initial clinical diagnosis was poorly differentiated adenocarcinoma of the descending colon, cT2N0M0, cStage I. Laparoscopic partial colectomy of the descending colon with D3 lymph node dissection and intracorporeal overlap anastomosis was performed. The pathological diagnosis however, returned mixed adenocarcinoma-neuroendocrine carcinoma (MANEC) of the descending colon, pT4aN1bM0, pStage IIIB, a subgroup of MiNEN: 70% was neuroendocrine carcinoma (NEC), whilst poorly differentiated mucinous carcinoma constituted 30% of the tumour. She completed 4 courses of irinotecan plus cisplatin (IP) adjuvant chemotherapy and is currently recurrence-free at postoperative year 2. The clinical course of MiNEN depends on the biology of the two components, both of which must be pathologically characterised. Even quantitatively discrete components should be carefully subtyped as their prognostic relevance is undetermined.

Clinicopathological Characteristics of Extrapulmonary Neuroendocrine Carcinomas: Treatment Responses and Survival Outcomes: Single-Center Experience

Background/Objectives: Extrapulmonary neuroendocrine carcinomas (EP-NECs) are rare, aggressive malignancies with no standardized treatment approach. Although platinum-based chemotherapy is considered the first-line therapy, overall survival (OS) and progression-free survival (PFS) remain limited. This study aims to evaluate the clinical and pathological characteristics of EP-NEC patients, their treatment responses, and survival outcomes. Methods: This retrospective observational study included 29 EP-NEC patients diagnosed and followed between 2015 and 2024. Clinical and demographic data, tumor localization, disease stage, administered treatments, and survival outcomes were analyzed. Kaplan-Meier survival analysis was used to assess OS and PFS, with subgroup comparisons performed via the log-rank test. Results: The most common primary tumor sites were the pancreas (21%), prostate (17%), and cervix (14%). At diagnosis, 55.2% of patients had metastatic disease. First-line platinum-based chemotherapy achieved an objective response rate of 82.1%, with a median PFS of 8.16 months and a median OS of 14.16 months. Surgical intervention significantly improved survival (p = 0.020), while a high Ki-67 proliferation index (>80%) was associated with worse PFS (p = 0.032). Other factors, including smoking status and liver-directed therapies, had no significant impact on survival. Conclusions: EP-NECs present with a poor prognosis despite platinum-based chemotherapy achieving high response rates. Surgical resection improves survival outcomes, whereas high Ki-67 expression is associated with a worse prognosis. These findings highlight the need for further research into novel therapeutic strategies for EP-NECs.

Mixed neuroendocrine non-neuroendocrine tumors: The quest for evidence

Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) are rare mixed tumors containing both neuroendocrine and non-neuroendocrine components that occupy at least 30% of the whole tumor. Biologically, both components appear to derive from an identical cellular precursor undergoing early dual differentiation or late transdifferentiation. While our understanding of MiNENs has improved in recent years, many areas of uncertainty remain. In this context, setting diagnostic criteria capable of capturing the continuum of disease biology while providing clinically meaningful information in terms of prognosis and response to treatments appears vital to advance the field and improve patients' outcomes. Evidence is needed to generate robust classification schemes, and multi-institutional cooperation will likely play a crucial role in building adequately powered cohorts to address some of the most pressing questions discussed in this Editorial. What is the minimum representation for each component needed to define MiNENs? How can the epidemiology of MiNENs change according to different diagnostic definitions? How can we generate the clinical evidence needed to optimize the management of MiNENs?

Characterizing esophageal mixed neuroendocrine-non-neuroendocrine neoplasms: insights from a retrospective multicenter study of clinical outcomes and prognostic indicators

Background

The esophageal mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) is an extremely rare but poor prognosis tumor.

Objectives

This retrospective study aimed to analyze the clinical characteristics of MiNEN and to investigate postoperative survival and prognostic factors.

Design

This retrospective study analyzed 69 patients diagnosed with esophageal MiNEN at two major esophageal cancer centers in China from January 2000 to December 2021.

Methods

We assessed demographic data, tumor characteristics, treatment modalities, and survival outcomes. Statistical analyses included Kaplan-Meier survival curves and Cox regression models to evaluate prognostic factors.

Results

The most common histological types were combinations of small-cell carcinoma and squamous carcinoma (91.3%). The correct diagnostic rate of preoperative pathologic biopsy was only 4.3%. The median overall survival (OS) was 24.0 months, and disease-free survival (DFS) was 16.6 months. The 1-, 3-, and 5-year survival rates were 84.1%, 34.8%, and 25.3%, respectively. A peak period of recurrence or metastasis occurs in the first year after surgery, and regional lymph node recurrence is the main route of postoperative recurrence or metastasis. Tumor size, T-stage, N-stage, and tumor, lymph node, metastasis (TNM) stage were significant prognostic factors. Subgroup analyses showed that in patients with limited-stage MiNEN in stages I-III, the postoperative adjuvant treatment modality failed to improve OS and DFS compared with surgery alone. Postoperative adjuvant therapy also failed to prolong OS and DFS in patients with lymph node-positive MiNEN. No significant survival benefits were observed with different surgical techniques or adjuvant chemotherapy regimens.

Conclusion

Esophageal MiNEN has aggressive behavior and a poor prognosis. In China, the pathologic type of esophageal MiNEN may be dominated by a combination of small-cell carcinoma and squamous carcinoma. Early-stage disease significantly correlated with improved survival outcomes. Current treatment protocols, similar to those for other esophageal cancers, show limited efficacy in improving patient survival.

[Neuroendocrine carcinomas of the gastrointestinal tract : Morphology, molecular pathology, cellular origin]

Neuroendocrine carcinomas (NEC) are poorly differentiated neuroendocrine neoplasms that can occur ubiquitously in the mucosa-bearing organs of the gastrointestinal tract. Based on their morphology, they are classified into large cell (LCNEC) and small cell NEC (SCNEC). The most common form of mixed differentiation is the combination with an adenocarcinoma, referred to as mixed adenoneuroendocrine carcinoma (MANEC). NEC/MANEC exhibit a significantly poorer prognosis than the adenocarcinomas of their respective primary sites, which is inextricably linked to their typical histomorphology. Adenocarcinomas with aberrant expression of neuroendocrine markers do not show a worse clinical course. Molecularly, NEC/MANEC have a profile comparable to the adenocarcinomas of their site of origin and a profile divergent from neuroendocrine tumors. Analyses of gastric NEC/MANEC have shown frequent MYC amplifications, which are reflected in MYC signatures in various transcriptome analyses.The cellular origin of NEC remains a subject of controversial discussion. New insights are provided by a MYC-driven, genetically modified mouse model that led to the development of large gastric tumors. These tumors were histologically identified as LCNEC and were accompanied by both neuroendocrine and non-neuroendocrine precursor lesions. Using immunofluorescence, a derivation from resident neuroendocrine cells in the gastric corpus was demonstrated, suggesting that at least a portion of LCNEC may originate directly from neuroendocrine cells.

Immune checkpoint inhibitor therapy for primary neuroendocrine carcinoma of the gallbladder: A case report and literature review

RATIONALE

Gallbladder neuroendocrine carcinoma (GNEC) is indeed a relatively rare malignant tumor of the gallbladder with neuroendocrine differentiation and the ability to produce and secrete a number of neurotransmitters and hormones, characteristics that make its clinical presentation and biological behavior likely to be different from those of other types of gallbladder cancer. Current treatment mostly relies on surgery and adjuvant chemotherapy and radiotherapy.

PATIENT CONCERNS

We report a 53-year-old middle-aged male patient who underwent radical surgery for gallbladder malignancy after a diagnosis of neuroendocrine carcinoma of the gallbladder.

DIAGNOSES

Diagnosis of neuroendocrine carcinoma of the gallbladder based on the return of pathologic findings.

INTERVENTION

After local progression of postoperative chemotherapy with the first-line regimen of etoposide + cisplatin, an immune checkpoint inhibitor (traplizumab) + FOLIFIRI (fluorouracil + calcium folinate + irinotecan) regimen was used.

OUTCOMES

The patient achieved 20 months of clinical survival and ultimately died of myelosuppression.

LESSONS

The use of immune checkpoint inhibitors may become an effective tool in the treatment of neuroendocrine carcinoma of the gallbladder.

Differentially Expressed Somatostatin (SST) and Its Receptors (SST1-5) in Sporadic Colorectal Cancer and Normal Colorectal Mucosa

BACKGROUND/OBJECTIVES

Colorectal cancer (CRC) is one of the most common human malignancies worldwide. The somatotropin-releasing inhibitory factor/somatostatin (SRIF/SST) acts through activation of five membrane receptors (SSTRs, SST1-5). The diagnostic and prognostic role of these peptides in sporadic CRC remains unclear. This study aimed to determine the role of tissue expression of SST and all SSTRs in the pathogenesis, diagnosis, and prognosis of sporadic CRC.

METHODS

The expression of SST and all SSTRs was assessed in the tissues of CRC patients, control colorectal mucosa and lymph node metastasis from the same patients using real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC).

RESULTS

Decreased SST (mRNA and peptide) and higher SST2 and SST5 (mRNA and peptide) expression in CRC vs. control was noted. A negative correlation between SST mRNA expression and patient's age in CRC and control groups were observed. IHC study confirmed the coexpression of SSTRs in all tissue groups and significant dependence on the cellular localization. Immunoexpression of SST2 and SST3 showed the most correlations with clinicopathological data in CRC patients. Interestingly, only control tissue showed differences in SST1-5 expression depending on the colon segment.

CONCLUSIONS

Reduced SST expression in CRC indicates a weakening in its antitumor effect in this cancer in vivo. Overexpression of SST2 and SST5 in CRC suggests that these receptors play an important role in the pathogenesis of this cancer. Analysis of SST1-5 tissue expression allows for differentiation between the mucinous and nonmucinous CRC subtypes. The coexpression of all SST1-5 and overexpression of not only SST2 and SST5 in CRC may have applications for future therapy based on the SRIF system in sporadic CRC.

Distinctive Phenotypic and Microenvironmental Characteristics of Neuroendocrine Carcinoma and Adenocarcinoma Components in Gastric Mixed Adenoneuroendocrine Carcinoma

This study aimed to conduct an in-depth examination of gene expression and microenvironmental profiles of gastric neuroendocrine carcinoma (NEC) and mixed adeno-NEC (MANEC). Tissue microarrays from 55 patients with gastric MANEC (N = 32) or NEC (N = 23) were analyzed using digital spatial profiling (GeoMx DSP, NanoString Technologies). Representative regions of interest were selected from the adenocarcinoma (ADC) portion (ADC-MANEC) and the NEC portion (NEC-MANEC) of the MANEC cores, and pure NEC (pNEC) cores. All regions of interest were separated into epithelial components and stromal components using the masking procedure in the GeoMx platform, followed by transcriptome analysis. Comparison of gene expression between ADC-MANEC and NEC-MANEC/pNEC identified several differentially expressed genes in the epithelial (including PEG10, MAP1B, STMN3, and AKT3) and stromal (FN1, COL1A1, SPARC, and BGN) components. Gene set enrichment analysis revealed that pathways related to the E2F target and G2M checkpoint were more enriched in NEC-MANEC and pNEC than in ADC-MANEC. Deconvolution analysis showed that the microenvironmental profile varied according to histologic differentiation. In ADC-MANEC, intraepithelial infiltrating immune cells were relatively more numerous, whereas fibroblasts in the stroma were more abundant in NEC-MANEC and pNEC. This study confirmed the distinct expression profile of each histologic component of MANEC according to its tumor vs stromal compartment using the DSP platform. Although each component of MANEC shares the same genetic origin, distinctive phenotypes should not be overlooked when managing patients with MANEC. This study provides a useful validation data set for future studies.

Clinicopathologic and Molecular Characterization of Inflammatory Bowel Disease-Associated Neuroendocrine Carcinomas and Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms

The pathogenesis of neuroendocrine carcinomas (NECs) and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) in the gastrointestinal tract remains poorly understood. This study aims to characterize the clinicopathologic and molecular features of NEC/MiNEN in patients with inflammatory bowel disease (IBD). Eighteen surgically resected IBD-associated intestinal carcinomas with a minimum of 30% neuroendocrine component were collected from 6 academic centers and compared with a control group of 12 IBD-associated carcinomas lacking neuroendocrine differentiation. Both groups exhibited a male predominance and similar age distribution. The NEC/MiNEN group was more likely to have a higher percentage of Crohn disease (9/18 vs 1/12; P = .024), occur in the rectum (9/18 vs 3/12) and small intestine (4/18 vs 0/12) (P < .01), be diagnosed on resection without a preceding biopsy (6/18 vs 0/12; P = .057), and have unidentifiable precursor lesions (10/18 vs 1/12; P = .018) than the control group. Synchronous carcinoma, advanced tumor stage (pT3 and pT4), and lymph node metastasis occurred at similar rates; however, the NEC/MiNEN group had a higher incidence of angiovascular invasion (14/18 vs 4/12; P = .024), distant metastasis (8/18 vs 1/12; P = .049), mortality (8/18 vs 2/12; P = .058), and worse survival (Kaplan-Meier; P = .023) than the control group. All tested cases were mismatch repair proficient. A Ki-67 proliferation index ranged from 25% to 100%. Next-generation sequencing in 11 NEC/MiNEN cases revealed low tumor mutational burdens but complex genetic abnormalities commonly involving TP53 (9/11; 82%), FBXW7 (4/11; 36%), and APC (3/11; 27%) genes, with the other genetic alterations randomly occurring in 1 or 2 cases. The neuroendocrine component, which shared similar molecular alterations as the nonneuroendocrine component, was subcategorized into intermediate (G3a) and high grade (G3b); the higher grade correlated with more genetic alterations. In conclusion, IBD-associated NEC/MiNEN shows diverse histologic features, variable precursor lesions, intricate genetic abnormalities, and aggressive biologic behavior. The classification and grading of gastrointestinal NEC/MiNEN may be refined for better clinical management.

An Italian real-world multicenter study of patients with advanced mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) of the gastro-entero-pancreatic system treated with chemotherapy

PURPOSE

The aim of this study is to describe the clinical management of an Italian series of patients with advanced gastro-entero-pancreatic (GEP) MiNENs treated in clinical practice.

METHODS

Clinical records of patients from four Italian referral Centers were retrospectively analyzed to correlate clinical/biological data with clinical outcomes. All the surgical specimens were centrally reviewed.

RESULTS

Clinical data and surgical samples of 51 patients during 1995-2015 were analyzed. Sites of origin were: 32 colorectal, 14 gastro-esophageal, and 5 pancreatobiliary. Twenty-one out of fifty-one (42.2%) developed metachronous distant metastases. Only 5/51 (9.8%) patients received peri-operative therapy, and 23/51 (45.1%) first-line chemotherapy, mostly fluoropyrimidines/oxaliplatin. The NEN component was poorly differentiated in the whole population. Patients with Ki67 index < 55% in the NEC component had a significantly longer median overall survival (OS) (35.3 months; 95% CI 27.1-41.0) than those with Ki67 ≥ 55% (11.9 months; 95% CI 9.1-14.0) P = 0.0005. The median OS was 14 months (95% CI 10.1-19.1) in the whole cohort, with 11.4 months (95% CI 6.2-20.2) in patients who received a first-line therapy.

CONCLUSION

This study confirms that GEP-MiNENs represent a complex disease and that over the past years the clinical management has been predominantly guided by the subjective judgment of the clinicians. Although, in this series, the NEC component appeared mostly responsible for the systemic spread and prognosis on the whole neoplasm, the lack of strong prognostic and predictive factors universally recognized seems to condition their management so far. Future prospective clinical and biomolecular studies could help clinicians to improve clinical management of GEP-MiNENs.

TROP2 in colorectal carcinoma: associations with histopathology, molecular phenotype, and patient prognosis

Antibody-drug conjugates (ADCs) directed to trophoblast cell surface antigen 2 (TROP2) have gained approval as a therapeutic option for advanced triple-negative breast cancer, and TROP2 expression has been linked to unfavourable outcomes in various malignancies. In colorectal carcinoma (CRC), there is still a lack of comprehensive studies on its expression frequency and its prognostic implications in relation to the main clinicopathological parameters. We examined the expression of TROP2 in a large cohort of 1,052 CRC cases and correlated our findings with histopathological and molecular parameters, tumour stage, and patient outcomes. TROP2 was heterogeneously expressed in 214/1,052 CRCs (20.3%), with only a fraction of strongly positive tumours. TROP2 expression significantly correlated with an invasive histological phenotype (e.g. increased tumour budding/aggressive histopathological subtypes), advanced tumour stage, microsatellite stable tumours, and p53 alterations. While TROP2 expression was prognostic in univariable analyses of the overall cohort (e.g. for disease-free survival, p < 0.001), it exhibited distinct variations among important clinicopathological subgroups (e.g. right- versus left-sided CRC, microsatellite stable versus unstable CRC, Union for International Cancer Control [UICC] stages) and lost its significance in multivariable analyses that included stage and CRC histopathology. In summary, TROP2 is quite frequently expressed in CRC and associated with an aggressive histopathological phenotype and microsatellite stable tumours. Future clinical trials investigating anti-TROP2 ADCs should acknowledge the observed intratumoural heterogeneity, given that only a subset of TROP2-expressing CRC show strong positivity. The prognostic implications of TROP2 are complex and show substantial variations across crucial clinicopathological subgroups, thus indicating that TROP2 is a suboptimal parameter to predict patient prognosis.

[Histo- and molecular pathology in gastroenteropancreatic neuroendocrine neoplasms]

Neuroendocrine neoplasms are classified according to the WHO classification based on morphological criteria into neuroendocrine tumors, neuroendocrine carcinomas, and mixed neuroendocrine-non-neuroendocrine neoplasms. Neuroendocrine tumors are well differentiated neoplasms and show characteristic site-specific histological and molecular features, which is important for their clinical management. In cases dealing with metastasis, pathology often can help to identify the primary tumors using a small immunohistochemical marker panel. Neuroendocrine carcinomas are poorly differentiated neoplasms. They are subdivided into neuroendocrine carcinomas of small cell and large cell type. The molecular profile of neuroendocrine carcinomas and mixed neuroendocrine-non-neuroendocrine neoplasms shows a close relationship to conventional adenocarcinomas with site-specific features. Molecular analysis of neuroendocrine carcinomas and neuroendocrine-non-neuroendocrine neoplasms are not yet fully integrated in daily diagnostics and are mainly performed in the context of precision oncology.

Histology Shift in Esophageal Cancer Between Biopsies and Resections After Neoadjuvant Therapy: A Pilot Study

Preoperative neoadjuvant therapy followed by resection is the mainstay treatment for locally advanced esophageal adenocarcinoma. We recently observed the histology shift from predominant esophageal adenocarcinoma in the biopsy to neuroendocrine neoplasm with or without adenocarcinoma in the post-treatment resection. The underlying mechanism of this finding is uncertain, and there is limited information in the literature. A total of 11 patients were identified: 10 patients received presurgical chemoradiation and 1 with chemotherapy. All biopsies were diagnosed with adenocarcinoma. When neuroendocrine immunomarkers were retrospectively performed on 5 biopsies, 2 showed focal positivity, although the classic neuroendocrine morphology was not readily appreciated. All resections contained neuroendocrine neoplasm, including 8 of well-differentiated type and 3 of neuroendocrine carcinomas. Two post-treatment esophagectomies consisted of neuroendocrine neoplasm only without residual adenocarcinoma. Upon follow-up, 8 patients died of the disease (median survival = 26 months), and 3 patients were alive after a median follow-up of 14 months. The overall median survival time was better than the reported esophageal neuroendocrine carcinoma (15 months). The 5-year observed survival rate was 11.3%, which was lower than the Surveillance, Epidemiology, and End Results 5-year survival rate of adenocarcinoma (21.8%). We reported a small series of esophageal adenocarcinoma that showed histology shift between biopsy and esophagectomy after neoadjuvant therapy. Our limited data suggest that prognosis of this group is different than the conventional adenocarcinoma. Awareness of this morphological change reminds pathologists to examine the biopsy specimens thoroughly, because recognition of neuroendocrine neoplasm, especially high-grade neuroendocrine component, might potentially affect pre- and post-surgical regimens.

Preoperative Diagnostic Dilemma in Rapidly Progressive Mixed Neuroendocrine-Nonendocrine Neoplasm of the Ascending Colon: A Case Report

Introduction: Mixed neuroendocrine-nonendocrine neoplasms (MiNENs) of the digestive tract are rare. They contain both neuroendocrine and nonendocrine components. We here report a rare case of a metastatic MiNEN originating in the ascending colon. Case Presentation: An 80-year-old man presented with abdominal pain and vomiting. Colonoscopy showed an obstructing mass in the ascending colon, and a biopsy resulted in diagnosis of an adenocarcinoma. A CT scan revealed multiple liver metastases. Thus, our diagnosis was stage IV colon adenocarcinoma (cT4aN1bM1a according to TNM Classification of Malignant Tumors). The primary lesion was resected to alleviate symptoms. Histopathological and immunohistochemical examination revealed a well-differentiated adenocarcinoma and a small-cell neuroendocrine carcinoma, leading to the diagnosis of a MiNEN. The patient declined postoperative treatment and died approximately 2 months after the surgery. Conclusion: The incidence of MiNENs may be underestimated because they lack typical symptoms or imaging features and are therefore often only diagnosed after resection. Awareness of colonic MiNENs and further accumulation of cases are necessary to improve the outcomes.

Comprehensive genomic and transcriptomic characterization of high-grade gastro-entero-pancreatic neoplasms

BACKGROUND

High-grade gastro-entero-pancreatic neoplasms (HG GEP-NENs) can be stratified according to their morphology and Ki-67 values into three prognostic classes: neuroendocrine tumors grade 3 (NETs G3), neuroendocrine carcinomas with Ki-67 < 55% (NECs <55) and NECs with Ki-67 ≥ 55% (NECs ≥55).

METHODS

We analyzed a cohort of 49 HG GEP-NENs by targeted Next-Generation Sequencing (TrueSight Oncology 500), RNA-seq, and immunohistochemistry for p53, Rb1, SSTR-2A, and PD-L1.

RESULTS

Frequent genomic alterations affected TP53 (26%), APC (20%), KRAS and MEN1 (both 11%) genes. NET G3 were enriched in MEN1 (p = 0.02) mutations, while both NECs groups were enriched in TP53 (p = 0.001), APC (p = 0.002) and KRAS (p = 0.02) mutations and tumors with TMB ≥ 10 muts/Mb (p = 0.01). No differentially expressed (DE) gene was found between NECs <55% and NECs ≥55%, while 1129 DE genes were identified between NET G3 and NECs. A slight enrichment of CD4+ and CD8+ T cells in NECs and of cancer-associated fibroblasts and macrophages (M2-like) in NET G3. Multivariate analysis identified histologic type and Rb1 loss as independent prognostic factors for overall survival.

CONCLUSIONS

This study showed that GEP-NET G3 and GEP-NECs exhibit clear genomic and transcriptomic differences, differently from GEP-NECs <55% and GEP-NECs ≥55%, and provided molecular findings with prognostic and potentially predictive value.

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.

Mixed neuroendocrine non-neuroendocrine neoplasms in gastroenteropancreatic tract

Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) are a heterogeneous group of malignant neoplasms that can settle in the gastroenteropancreatic tract. They are composed of a neuroendocrine (NE) and a non-NE component in at least 30% of each tumour. The non-NE component can include different histological combinations of glandular, squamous, mucinous and sarcomatoid phenotypes, and one or both of the components can be low-or high grade malignant. Recent changes in the nomenclature of these neoplasms might lead to great deal of confusion, and the lack of specific clinical trials is the main reason why their management is difficult. The review aims to clarify the definition of MiNEN and analyze available evidence about their diagnosis and treatment options according to their location and extension through careful analysis of the available data. It would be important to reach a general consensus on their diagnosis in order to construct a classification that remains stable over time and facilitates the design of clinical trials that, due to their low incidence, will require long recruitment periods.

PITX2 as a Sensitive and Specific Marker of Midgut Neuroendocrine Tumors: Results from a Cohort of 1157 Primary Neuroendocrine Neoplasms

As neuroendocrine tumors (NETs) often present as metastatic lesions, immunohistochemical assignment to a site of origin is one of the most important tasks in their pathologic assessment. Because a fraction of NETs eludes the typical expression profiles of their primary localization, additional sensitive and specific markers are required to improve diagnostic certainty. We investigated the expression of the transcription factor Pituitary Homeobox 2 (PITX2) in a large-scale cohort of 909 NET and 248 neuroendocrine carcinomas (NEC) according to the immunoreactive score (IRS) and correlated PITX2 expression groups with general tumor groups and primary localization. PITX2 expression (all expression groups) was highly sensitive (98.1%) for midgut-derived NET, but not perfectly specific, as non-midgut NET (especially pulmonary/duodenal) were quite frequently weak or moderately positive. The specificity rose to 99.5% for a midgut origin of NET if only a strong PITX2 expression was considered, which was found in only 0.5% (one pancreatic/one pulmonary) of non-midgut NET. In metastases of midgut-derived NET, PITX2 was expressed in all cases (87.5% strong, 12.5% moderate), whereas CDX2 was negative or only weakly expressed in 31.3% of the metastases. In NEC, a fraction of cases (14%) showed a weak or moderate PITX2 expression, which was not associated with a specific tumor localization. Our study independently validates PITX2 as a very sensitive and specific immunohistochemical marker of midgut-derived NET in a very large collective of neuroendocrine neoplasms. Therefore, our data argue toward implementation into diagnostic panels applied for NET as a firstline midgut marker.

The State-of-the-Art Mechanisms and Antitumor Effects of Somatostatin in Colorectal Cancer: A Review

Somatostatin, a somatotropin release inhibiting factor (SST, SRIF), is a widely distributed multifunctional cyclic peptide and acts through a transmembrane G protein-coupled receptor (SST1-SST5). Over the past decades, research has begun to reveal the molecular mechanisms underlying the anticancer activity of this hormonal peptide. Among gastrointestinal tract (GIT) tumors, direct and indirect antitumor effects of SST have been documented best in gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and less well in non-endocrine cancers, including sporadic colorectal cancer (CRC). In the latter, the signaling pathways involved in the antitumor function of SST are primarily MAPK/ERK/AKT and Wnt/β-catenin. Direct (involving the MAPK pathway) and indirect (VEGF production) antiangiogenic effects of SST in CRC have also been described. The anti-inflammatory role of SST in CRC is emphasized, but detailed molecular mechanisms are still being explored. The role of SST in tumor genome/tumor microenvironment (TME)/host's gut microbiome interactions is only partially known. The results of SST analogues (SSAs)' treatment of sporadic CRC in monotherapy in vivo are not spectacular. The current review aims to present the state-of-the-art mechanisms and antitumor activity of endogenous SST and its synthetic analogues in CRC, with particular emphasis on sporadic CRC.

High expression of insulinoma-associated protein 1 (INSM1) distinguishes colorectal mixed and pure neuroendocrine carcinomas from conventional adenocarcinomas with diffuse expression of synaptophysin

Complementary to synaptophysin and chromogranin A, insulinoma-associated protein 1 (INSM1) has emerged as a sensitive marker for the diagnosis of neuroendocrine neoplasms. Since there are no comparative data regarding INSM1 expression in conventional colorectal adenocarcinomas (CRCs) and colorectal mixed adenoneuroendocrine carcinomas/neuroendocrine carcinomas (MANECs/NECs), we examined INSM1 in a large cohort of conventional CRCs and MANECs/NECs. In conventional CRC, we put a special focus on conventional CRC with diffuse expression of synaptophysin, which carry the risk of being misinterpreted as a MANEC or a NEC. We investigated INSM1 according to the immunoreactive score in our main cohort of 1,033 conventional CRCs and 21 MANECs/NECs in comparison to the expression of synaptophysin and chromogranin A and correlated the results with clinicopathological parameters and patient survival. All MANECs/NECs expressed INSM1, usually showing high or moderate expression (57% high, 34% moderate, and 9% low), which distinguished them from conventional CRCs, which were usually INSM1 negative or low, even if they diffusely expressed synaptophysin. High expression of INSM1 was not observed in conventional CRCs. Chromogranin A was negative/low in most conventional CRCs (99%), but also in most MANECs/NECs (66%). Comparable results were observed in our independent validation cohorts of conventional CRC (n = 274) and MANEC/NEC (n = 19). Similar to synaptophysin, INSM1 expression had no prognostic relevance in conventional CRCs, while true MANEC/NEC showed a highly impaired survival in univariate and multivariate analyses (e.g. disease-specific survival: p < 0.001). MANECs/NECs are a highly aggressive variant of colorectal cancer, which must be reliably identified. High expression of INSM1 distinguishes MANEC/NEC from conventional CRCs with diffuse expression of the standard neuroendocrine marker synaptophysin, which do not share the same dismal prognosis. Therefore, high INSM1 expression is a highly specific/sensitive marker that is supportive for the diagnosis of true colorectal MANEC/NEC.

Clinicopathologic and Molecular Characterization of Anorectal Neuroendocrine Carcinomas Reveals Human Papillomavirus, p53, and c-Myc as Alternative Mechanisms of Carcinogenesis

Poorly differentiated neuroendocrine carcinomas (NECs) are rare malignant neoplasms with aggressive behavior. The diagnosis remains challenging due to ever-changing terminologies and morphologic overlaps with other disease entities. Herein, we seek to better define anorectal NECs by high-risk human papillomavirus (HPV) status and molecular profiling. Fourteen cases, including 3 men and 11 women with a median age of 63 years, were included. High-risk HPV RNA in situ hybridization was diffusely positive (+) in 7 cases, focal rarely positive (+/-) in 2 cases, and completely negative (-) in 5 cases. By morphology, all HPV(-) NECs were large-cell type, 3 mixed with a tubular adenoma/dysplasia or invasive adenocarcinoma. HPV-related (+ or +/-) NECs were mostly small-cell type, 3 mixed with squamous dysplasia and/or squamous cell carcinoma. Immunohistochemically, all NECs were positive for at least 2 neuroendocrine markers. The HPV(-) NECs were also positive for CDX2, whereas all HPV-related NECs were negative or only focally positive for CDX2, p40, and p63. Overexpression of p53 was found in 3 HPV(-) and 2 HPV(+/-) NECs but not in any HPV(+) NECs. Molecular analysis revealed MYC gene amplification in 4 cases: 2 HPV(-), 1 HPV(+/-), and 1 HPV(+). This was confirmed by fluorescence in situ hybridization in all but 1 HPV(-) NEC, which showed polysomy 8 but no true MYC amplification. Interestingly, only 2 of the 4 MYC amplification-bearing cases, both p53 normal/wild-type, expressed c-Myc protein by immunohistochemistry. The other 2 cases, both p53 overexpressed, did not show c-Myc expression despite true MYC amplification. Our study demonstrates that anorectal NECs arise in HPV-dependent or -independent pathways, with heterogeneous expression of other lineage markers and different molecular signatures. Expressions of p53 and c-Myc proteins appear to be mutually exclusive regardless of HPV status, likely mediating alternative mechanisms of NEC carcinogenesis.

Updates in histopathological classification and tissue biomarkers of digestive neuroendocrine neoplasms: What the clinician should know

Histopathological classifications of neuroendocrine neoplasms (NEN) change regularly and the latest WHO classification published in 2022, which concerns all NEN in the body, attempts to standardize classifications in the different locations. Differentiation and proliferation mainly assessed by Ki-67 index are still the cornerstone of those classifications. However, many markers are now used for diagnostic (to check neuroendocrine differentiation, to identify the site of origin of a metastasis, to help separating high-grade neuroendocrine tumors/NET and neuroendocrine carcinoma/NEC), prognostic or theranostic purposes. NENs are often heterogeneous and this can lead to difficulties in classifications, biomarker and prognostic assessment. These different points are discussed successively in this review, insisting especially on the frequent digestive, gastro-entero-pancreatic (GEP) localizations.

Precise microdissection of gastric mixed adeno-neuroendocrine carcinoma dissects its genomic landscape and evolutionary clonal origins

Gastric mixed adenoneuroendocrine carcinoma (MANEC) is a clinically aggressive and heterogeneous tumor composed of adenocarcinoma (ACA) and neuroendocrine carcinoma (NEC). The genomic properties and evolutionary clonal origins of MANEC remain unclear. We conduct whole-exome and multiregional sequencing on 101 samples from 33 patients to elucidate their evolutionary paths. We identify four significantly mutated genes, TP53, RB1, APC, and CTNNB1. MANEC resembles chromosomal instability stomach adenocarcinoma in that whole-genome doubling in MANEC is predominant and occurs earlier than most copy-number losses. All tumors are of monoclonal origin, and NEC components show more aggressive genomic properties than their ACA counterparts. The phylogenetic trees show two tumor divergence patterns, including sequential and parallel divergence. Furthermore, ACA-to-NEC rather than NEC-to-ACA transition is confirmed by immunohistochemistry on 6 biomarkers in ACA- and NEC-dominant regions. These results provide insights into the clonal origin and tumor differentiation of MANEC.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for digestive neuroendocrine carcinoma

This ENETS guidance paper, developed by a multidisciplinary working group, provides up-to-date and practical advice on the diagnosis and management of digestive neuroendocrine carcinoma, based on recent developments and study results. These recommendations aim to pave the road for more standardized care for our patients resulting in improved outcomes. Prognosis is generally poor for digestive NEC, most are advanced at diagnosis and median survival in metastatic disease is 11-12 months. Surgery can be of benefit for localized disease after extensive preoperative imaging. Carboplatin in combination with etoposide is recommended as first-line treatment for metastatic disease. Irinotecan with fluoropyrimidines has the best evidence as second-line treatment. Immunotherapy plays a minor role in biomarker-unselected patients. Molecular profiling if available is encouraged to identify new targets. More prospective clinical trials are highly needed to fulfil the unmet needs in this field, especially on new predictive and prognostic biomarkers and to improve survival of patients with advanced disease.

Comprehensive analysis of mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs): A SEER database analysis of 767 cases

Background

Mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN) is an extremely rare entity, consisting of neuroendocrine and non-neuroendocrine components. It can occur in various organs throughout the body, with a rising incidence. Its clinical management is a rapidly growing field of interest; however, large-scale patient cohorts are still missing to guide clinical practice.

Patients and methods

The demographic, clinicopathological, and survival information of all patients diagnosed with MiNEN in the national Surveillance, Epidemiology, and End Results (SEER) program database (2000-2017) were extracted and further analyzed. The information of the patients before and after 2010 was compared to understand the epidemiological changes of MiNEN. The characteristics of MiNEN originating in different organs were compared. The clinical significance of surgical resection for metastatic MiNENs was also analyzed.

Results

A total of 1081 patients were screened, and after applying the exclusion criteria, 767 patients were finally analyzed. There was no obvious sex preference (49.2% vs 50.8%, p>0.05) and the majority of the patients were Caucasians (n=627, 81.7%). A total of 88.3% of the patients were older than 50 years old, and the median age was 60 years. 79.3% of the tumors are located in the distal digestive tract, and 67.7% were grade 3/4. Distant metastasis was presented in 33.9% of the patients at diagnosis. A total of 88% of the patients underwent surgical treatments. The number of patients increased 10-fold between 2000 and 2017. There was no significant difference in sex, race, stage, or surgical treatments among the patients diagnosed before and after 2010. More patients older than 60 years were diagnosed after 2010 (p=0.009). The median survival was 61.0 ± 9.8 months for the whole cohort. After multivariate analysis, older age (>60 years, p<0.01), more advanced stage (p<0.01), grade 3/4 (p<0.01), and non-surgical treatment (p<0.01) were independent risk factors for poorer survival. The appendiceal MiNENs showed the best prognosis. A total of 260 metastatic MiNENs were further analyzed. Only patients with metastatic MiNENs originating from the appendix had a potential benefit from surgical resection, compared to other sites (p=0.05).

Conclusion

This study provides the epidemiological, clinicopathological, and survival information of the largest number of MiNEN patients. Although MiNEN is an extremely rare malignant neoplasm, its incidence increases rapidly. The majority of the patients suffered from advanced-stage disease, which highlights the need for improvement of early detection in the future. The appendix is the most common primary site of MiNEN, and surgical resection for selected metastatic MiNEN originating in the appendix has favorable survival outcomes.

Genomic characterization reveals distinct mutation landscapes and therapeutic implications in neuroendocrine carcinomas of the gastrointestinal tract

BACKGROUND

Neuroendocrine carcinomas of the gastrointestinal tract (GI-NECs) remain a disease of grim prognosis with limited therapeutic options. Their molecular characteristics are still undefined. This study aimed to explore the underlying genetic basis and heterogeneity of GI-NECs.

METHODS

Comprehensive genomic analysis using whole-exome sequencing was performed on 143 formalin-fixed, paraffin-embedded samples of surgically resected GI-NEC with a thorough histological evaluation. Mutational signatures, somatic mutations, and copy number aberrations were analyzed and compared across anatomic locations and histological subtypes. Survival analysis was conducted to identify the independent factors.

RESULTS

In total, 143 GI-NECs were examined: the stomach, 87 cases (60.8%); the esophagus, 29 cases (20.3%); the colorectum, 20 cases (14.0%); and the small intestine, 7 cases (4.9%). Eighty-three (58.0%) and 60 (42.0%) cases were subclassified into small cell and large cell subtypes, respectively. GI-NECs showed distinct genetic alterations from their lung counterparts and non-neuroendocrine carcinomas in the same locations. Obvious heterogeneity of mutational signatures, somatic mutations, and copy number variations was revealed across anatomic locations rather than histological subtypes. Except for tumor protein p53 (TP53) and retinoblastoma 1 (RB1), the most frequently mutated genes in the stomach, esophagus, colorectum, and small intestine were low-density lipoprotein receptor-related protein 1B (LRP1B), notch receptor 1 (NOTCH1), adenomatosis polyposis coli (APC), catenin beta 1 (CTNNB1), respectively. Mutations in the WNT-β-catenin, NOTCH and erythroblastic leukemia viral oncogene B (ERBB) pathways were prevalently identified in gastric, esophageal, and colorectal NECs, respectively. Importantly, 104 (72.7%) GI-NECs harbored putative clinically relevant alterations, and non-gastric location and RB1 bi-allelic inactivation with copy number alterations were identified as two independent poor prognostic factors. Furthermore, we found that tumor cells in GI-NECs first gain clonal mutations in TP53, RB1, NOTCH1 and APC, followed by subsequent whole-genome doubling (WGD) and post-WGD clonal mutations in LRP1B, CUB and Sushi multiple domains 3 (CSMD3), FAT tumor suppressor homolog 4 (FAT4) and erb-b2 receptor tyrosine kinase 4 (ERBB4), and finally develop subclonal mutations.

CONCLUSIONS

GI-NECs harbor distinct genomic landscapes and demonstrate significant genetic heterogeneity across different anatomic locations. Moreover, potentially actionable alterations and prognostic factors were revealed for GI-NECs.

Exploratory genomic analysis of high-grade neuroendocrine neoplasms across diverse primary sites

High-grade (grade 3) neuroendocrine neoplasms (G3 NENs) have poor survival outcomes. From a clinical standpoint, G3 NENs are usually grouped regardless of primary site and treated similarly. Little is known regarding the underlying genomics of these rare tumors, especially when compared across different primary sites. We performed whole transcriptome (n = 46), whole exome (n = 40), and gene copy number (n = 43) sequencing on G3 NEN formalin-fixed, paraffin-embedded samples from diverse organs (in total, 17 were lung, 16 were gastroenteropancreatic, and 13 other). G3 NENs despite arising from diverse primary sites did not have gene expression profiles that were easily segregated by organ of origin. Across all G3 NENs, TP53, APC, RB1, and CDKN2A were significantly mutated. The CDK4/6 cell cycling pathway was mutated in 95% of cases, with upregulation of oncogenes within this pathway. G3 NENs had high tumor mutation burden (mean 7.09 mutations/MB), with 20% having >10 mutations/MB. Two somatic copy number alterations were significantly associated with worse prognosis across tissue types: focal deletion 22q13.31 (HR, 7.82; P = 0.034) and arm amplification 19q (HR, 4.82; P = 0.032). This study is among the most diverse genomic study of high-grade neuroendocrine neoplasms. We uncovered genomic features previously unrecognized for this rapidly fatal and rare cancer type that could have potential prognostic and therapeutic implications.

From morphology to molecular targets—the pathologist’s view in diagnosing gastroenteropancreatic neuroendocrine neoplasms

In the last decade, a number of genetic alterations in gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) have been identified. In addition, differences in tumor morphology as well as proliferation index (Ki-67) or number of mitoses have led to changes in the classification of these neoplasms. According to the new World Health Organization (WHO) classification, GEP-NENs are now divided into two genetically and prognostically different categories: (i) well-differentiated neuroendocrine tumors (NET) subdivided into low (G1), intermediate (2) and high (G3) grade tumors, and (ii) poorly differentiated neuroendocrine carcinomas (NEC). In addition, a group of mixed neuroendocrine–non-neuroendocrine neoplasms (MiNEN) has been defined. This review focuses on the clinical, morphological, immunohistochemical and molecular findings of the GEP-NENs and their key diagnostic features that can help the pathologist to differentiate between tumors in this heterogeneous group. In challenging cases, additional immunohistochemical and/or molecular analysis can be helpful to determine the correct diagnosis and proper treatment for the patient.

Morphologic and Molecular Heterogeneity of Cervical Neuroendocrine Neoplasia: A Report of 14 Cases

Neuroendocrine neoplasms (NENs) of the cervix are rare aggressive tumors associated with poor prognosis and only limited treatment options. Although there is some literature on molecular underpinnings of cervical small cell neuroendocrine carcinomas (SCNECs), detailed morphologic and associated molecular characteristics of cervical NENs remains to be elucidated. Herein, 14 NENs (SCNEC: 6, large cell neuroendocrine carcinoma [LCNEC]: 6, neuroendocrine tumor [NET]: 2), including 5 admixed with human papillomavirus (HPV)-associated adenocarcinoma (carcinoma admixed with neuroendocrine carcinoma) were analyzed. All except 3 SCNECs were HPV16/18 positive. TP53 (3) and/or RB1 (4) alterations (3 concurrent) were only seen in SCNECs (4/6) and were enriched in the HPV16/18-negative tumors. The other most common molecular changes in neuroendocrine carcinomas (NECs) overlapping with those reported in the literature for cervical carcinomas involved PI3K/MAPK pathway (4) and MYC (4) and were seen in both SCNECs and LCNECs. In contrast, the 2 NETs lacked any significant alterations. Two LCNECs admixed with adenocarcinoma had enough material to sequence separately each component. In both pathogenic alterations were shared between the 2 components, including ERBB2 amplification in one and an MSH6 mutation with MYC amplification in the other. Overall, these findings suggest that cervical HPV-associated NETs are genomically silent and high-grade NECs (regardless of small or large cell morphology) share molecular pathways with common cervical carcinomas as it has been reported in the endometrium and are different from NECs at other sites. Molecular analysis of these highly malignant neoplasms might inform the clinical management for potential therapeutic targets.

Establishment and validation of a clinicopathological prognosis model of gastroenteropancreatic neuroendocrine carcinomas

Background

Gastroenteropancreatic neuroendocrine carcinomas (GEP-NECs) are a rare, highly malignant subset of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). However, how to predict the prognosis of GEP-NECs by clinical features is still under study. This study aims to establish and validate a nomogram model of overall survival (OS) in patients with GEP-NECs for predicting their prognosis.

Methods

We selected patients diagnosed with GEP-NECs from the Surveillance, Epidemiology, and End Results (SEER) database and two Chinese hospitals. After randomization, we divided the data in the SEER database into the train cohort and the test cohort at a ratio of 7:3 and used the Chinese cohort as the validation cohort. The Cox univariate and multivariate analyses were performed to incorporate statistically significant variables into the nomogram model. We then established a nomogram and validated it by concordance index (C-index), calibration curve, receiver operating characteristic (ROC) curve, the area under the curve (AUC), and the decision curve analysis (DCA) curve.

Results

We calculated the nomogram C-index as 0.797 with a 95% confidence interval (95% CI) of 0.783–0.815 in the train cohort, 0.816 (95% CI: 0.794–0.833) in the test cohort and 0.801 (95% CI: 0.784–0.827) in the validation cohort. Then, we plotted the calibration curves and ROC curves, and AUCs were obtained to verify the specificity and sensitivity of the model, with 1-, 3- and 5-year AUCs of 0.776, 0.768, and 0.770, respectively, in the train cohort; 0.794, 0.808, and 0.799 in the test cohort; 0.922, 0.925, and 0.947 in the validation cohort. The calibration curve and DCA curves also indicated that this nomogram model had good clinical benefits.

Conclusions

We established the OS nomogram model of GEP-NEC patients, including variables of age, race, sex, tumor site, tumor grade, and TNM stage. This model has good fitting, high sensitivity and specificity, and good clinical benefits.

Molecular Subtypes of Extra-pulmonary Neuroendocrine Carcinomas Identified by the Expression of Neuroendocrine Lineage-Specific Transcription Factors

Extra-pulmonary neuroendocrine carcinomas (EPNEC) represent a group of rare and heterogenous neoplasms with adverse clinical outcome. Their molecular profile is largely unexplored. Our aim was to investigate if the major transcriptional drivers recently described in high-grade pulmonary neuroendocrine carcinomas characterize distinct molecular and clinical subgroups of EPNEC. Gene expression of ASCL1, NEUROD1, DLL3, NOTCH1, INSM1, MYCL1, POU2F3, and YAP1 was investigated in a series of 54 EPNEC (including 10 cases with mixed components analyzed separately) and in a group of 48 pulmonary large cell neuroendocrine carcinomas (P-LCNEC). Unsupervised hierarchical cluster analysis classified the whole series into four major clusters. P-LCNEC were classified into two major clusters, the first ASCL1/DLL3/INSM1-high and the second (including four EPNEC) ASCL1/DLL3-low but INSM1-high. The remaining EPNEC cases were sub-classified into two other clusters. The first showed INSM1-high and alternative ASCL1/DLL3 or NEUROD1 high expression. The second was characterized mainly by MYCL1 and YAP1 overexpression. In the ten cases with mixed histology, ASCL1, DLL3, INSM1, and NEUROD1 genes were significantly upregulated in the neuroendocrine component. Higher gene-expression levels of NOTCH1 and INSM1 were associated with lower pT stage and negative nodal status. Low INSM1 gene expression was associated with shorter overall survival in the entire case series (p = 0.0017) and with a trend towards significance in EPNEC, only (p = 0.06). In conclusion, our results show that EPNEC possess distinct neuroendocrine-lineage-specific transcriptional profiles; moreover, low INSM1 gene expression represents a novel potential unfavorable prognostic marker in high-grade NECs including those in extra-pulmonary location.

Identification of functional pathways and molecular signatures in neuroendocrine neoplasms by multi-omics analysis

BACKGROUND

Neuroendocrine neoplasms (NENs) represent a heterogeneous class of rare tumors with increasing incidence. They are characterized by the ability to secrete peptide hormones and biogenic amines but other reliable biomarkers are lacking, making diagnosis and identification of the primary site very challenging. While in some NENs, such as the pancreatic ones, next generation sequencing technologies allowed the identification of new molecular hallmarks, our knowledge of the molecular profile of NENs from other anatomical sites is still poor.

METHODS

Starting from the concept that NENs from different organs may be clinically and genetically correlated, we applied a multi-omics approach by combining multigene panel testing, CGH-array, transcriptome and miRNome profiling and computational analyses, with the aim to highlight common molecular and functional signatures of gastroenteropancreatic (GEP)-NENs and medullary thyroid carcinomas (MTCs) that could aid diagnosis, prognosis and therapy.

RESULTS

By comparing genomic and transcriptional profiles, ATM-dependent signaling emerged among the most significant pathways at multiple levels, involving gene variations and miRNA-mediated regulation, thus representing a novel putative druggable pathway in these cancer types. Moreover, a set of circulating miRNAs was also selected as possible diagnostic/prognostic biomarkers useful for clinical management of NENs.

CONCLUSIONS

These findings depict a complex molecular and functional landscape of NENs, shedding light on novel therapeutic targets and disease biomarkers to be exploited.

Mixed neuroendocrine-non-neuroendocrine neoplasms of the digestive system: A mini-review

Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are rare mixed tumors containing both neuroendocrine (NE) and non-NE components. Each component must occupy at least 30% of the tumor volume by definition. Recent molecular evidence suggests MiNENs are clonal neoplasms and potentially harbor targetable mutations similar to conventional carcinomas. There have been multiple changes in the nomenclature and classification of MiNENs which has created some confusion among pathologists on how to integrate the contributions of each component in a MiNEN, an issue which in turn has resulted in confusion in communication with front-line treating oncologists. This mini review summarizes our current understanding of MiNENs and outline diagnosis, prognosis, and management of these neoplasms. The authors emphasize the importance of treating the most aggressive component of the tumor regardless of its percentage volume.

Mixed Neuroendocrine Non-Neuroendocrine Neoplasms of the Gastrointestinal Tract: A Case Series

Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) refer to heterogenous rare neoplasms constituted of at least a neuroendocrine population—either well-differentiated, or more frequently poorly differentiated—and a non-neuroendocrine population, both accounting for at least 30% of the whole tumor mass. Several studies recently focused on the key genetic and epigenetic changes underlying MiNENs to better understand how they develop, and explore biological similarities among the two components and their pure counterparts. However, their molecular landscape still remains poorly understood. NGS may represent a useful tool to study this orphan disease by detecting the main genetic alterations and possible therapeutic targets. NGS analysis on tissue and/or blood samples through the Foundation One (F1) platform was performed on consecutive samples collected from four patients diagnosed with MiNENs of the gastroenteric tract. Several genetic alterations were shared among samples from the same patients, thus suggesting a common origin between them, although morphology sometimes changed at histopathological evaluation. Common molecular alterations among samples from different patients that had not been previously described to our knowledge were also detected. Finally, it is of the utmost importance to clarify if the maintenance of the 30% cut-off is still essential in defining MiNENs and really manages to include all of the mixed neoplasms.

An update on the development of concepts, diagnostic criteria, and challenging issues for neuroendocrine neoplasms across different digestive organs

Digestive neuroendocrine neoplasms (NENs) are a group of heterogeneous neoplasms found throughout the digestive tract, with different behaviour and genetic background. In the last few years, nomenclature and WHO/UICC classifications of digestive NENs have changed, and molecular classifications have emerged, especially in pancreatic locations. Increasing patho-molecular details are needed to diagnose the different categories of NEN, including the use of helpful immunohistochemical markers. In this review, we address these topics in three successive chapters. We first briefly review recent updates in classifications, discuss important grading and proliferating issues and advances in the molecular understanding of NEN. Then, we provide an update on diagnosis, including the most important differential diagnoses of NEN, with a focus on high-grade neoplasms and mixed tumours. Finally, we highlight a variety of currently used and next-generation predictive and prognostic biomarkers as well as biomarkers of tumour origin and describe some site specificities of gastrointestinal NEN. We specifically focus on biomarkers available to pathologists with the potential to change the way patients with NEN are diagnosed and treated.

Mixed neuroendocrine-nonneuroendocrine neoplasms of the gastrointestinal system: An update

Mixed neuroendocrine-nonneuroendocrine neoplasms (MiNENs) of the digestive tract are a rare heterogeneous group of tumors that present many challenges in terms of diagnosis and treatment. Over the years, the diagnostic criteria, classification, and clinical behavior of these tumors have been the subjects of ongoing debate, and the various changes in their nomenclature have strengthened the challenges associated with MiNENs. This review is performed to provide an understanding of the key factors involved in the evolution of the designation of these tumors as MiNEN, highlight the current diagnostic criteria, summarize the latest data on pathogenesis and provide information on available treatments. Moreover, this work seeks to increase the awareness about these rare neoplasms by presenting the clinicopathological features and prognostic factors that play important roles in their behavior and discussing their different regions of origin in the gastrointestinal system (GIS). Currently, the MiNEN category also includes tumors in the GIS with a nonneuroendocrine component and epithelial tumors other than adenocarcinoma, depending on the organ of origin. Diagnosis is based on the presence of both morphological components in more than 30% of the tumor. However, this value needs to be reconfirmed with further studies and may be a limiting factor in the diagnosis of MiNEN by biopsy. Furthermore, available clinicopathological data suggest that the inclusion of amphicrine tumors in the definition of MiNEN is not supportive and warrants further investigation. The diagnosis of these tumors is not solely based on immunohistochemical findings. They are not hybrid tumors and both components can act independently; thus, careful grading of each component separately is required. In addition to parameters such as the metastatic state of the tumor at the time of diagnosis and the feasibility of surgical resection, the aggressive potential of both components has paramount importance in the choice of treatment. Regardless of the organ of origin within the GIS, almost MiNENs are tumors with poor prognosis and are frequently encountered in the elderly and men. They are most frequently reported in the colorectum, where data from molecular studies indicate a monoclonal origin; however, further studies are required to provide additional support for this origin.

MUC1-C dictates neuroendocrine lineage specification in pancreatic ductal adenocarcinomas

Pancreatic ductal adenocarcinomas (PDAC) and poorly differentiated pancreatic neuroendocrine (NE) carcinomas are KRAS mutant malignancies with a potential common cell of origin. PDAC ductal, but not NE, lineage traits have been associated with cell-intrinsic activation of interferon (IFN) pathways. The present studies demonstrate that the MUC1 C-terminal subunit (MUC1-C), which evolved to protect mammalian epithelia from loss of homeostasis, is aberrantly overexpressed in KRAS mutant PDAC tumors and cell lines. We show that MUC1-C is necessary for activation of the type I and II IFN pathways and for expression of the Yamanaka OCT4, SOX2, KLF4 and MYC (OSKM) pluripotency factors. Our results demonstrate that MUC1-C integrates IFN signaling and pluripotency with NE dedifferentiation by forming a complex with MYC and driving the (i) achaete-scute homolog 1 and BRN2/POU3F2 neural, and (ii) NOTCH1/2 stemness transcription factors. Of translational relevance, targeting MUC1-C genetically and pharmacologically in PDAC cells (i) suppresses OSKM, NE dedifferentiation and NOTCH1/2, and (ii) inhibits self-renewal capacity and tumorigenicity. In PDAC tumors, we show that MUC1 significantly associates with activation of IFN signaling, MYC and NOTCH, and that upregulation of the MUC1-C → MYC pathway confers a poor prognosis. These findings indicate that MUC1-C dictates PDAC NE lineage specification and is a potential target for the treatment of recalcitrant pancreatic carcinomas with NE dedifferentiation.

p53 Immunohistochemistry Patterns Are Surrogate Biomarkers for TP53 Mutations in Gastrointestinal Neuroendocrine Neoplasms

Aims. The aim of this study was to establish p53 immunohistochemistry (IHC) patterns to predict TP53 mutations in gastrointestinal neuroendocrine neoplasms (GI-NENs) and to determine whether p53 IHC patterns could be used for the differential diagnosis of neuroendocrine neoplasms. Methods. TP53 gene sequencing and p53 IHC were performed on formalin-fixed paraffin-embedded (FFPE) tissue samples from 92 patients diagnosed with GI-NENs from five medical centers. Results. The cohort included 35 well-differentiated neuroendocrine tumors and 57 poorly differentiated neuroendocrine carcinomas. Gene sequencing revealed 38 wild-type TP53 and 54 TP53 mutations. p53 expression was interpreted as follows: pattern A, p53 was absent from all tumor cells; pattern B, scattered and weak p53 expression in 1-20% of tumor cells; and pattern C was subclassified as pattern C1: variable p53 staining intensity in 21-60% of tumor cells and tumor cell nests with focal strong positive p53 staining and pattern C2: strong p53 staining in more than 60% of tumor cells. p53 IHC patterns were evaluated as a binary classifier where pattern B predicted wild-type TP53, and patterns A and C predicted TP53 mutations. The sensitivity, specificity, and overall accuracy of this binary classification to predict TP53 status were 0.963, 0.868, and 0.924, respectively. p53 IHC patterns were also correlated with TP53 mutation types. Most cases with pattern A harboured loss-of-function (LOF) mutations, whereas patterns B and C tended to indicate wild-type TP53 and gain-of-function (GOF) mutations, respectively. Furthermore, most of the well-differentiated NETs showed pattern B, whereas pattern C2 was more common in poorly differentiated NECs. Finally, staining interpretation between different observers also yielded high reproducibility. Conclusions. p53 IHC patterns may be used as predictors of TP53 gene mutations and therefore could be potential surrogate markers for TP53 mutations in GI-NENs and could distinguish between well-differentiated NETs and poorly differentiated NECs.

Mixed Pulmonary Adenocarcinoma and Atypical Carcinoid: A Report of Two Cases of a Non-codified Entity With Biological Profile

Pulmonary carcinoids combined with a non-neuroendocrine component have rarely been described, and this histological subtype is not included as a specific entity in the current World Health Organization classification of pulmonary neoplasms. Here, we described the molecular and histological features of two rare cases of mixed lung neoplasms, composed of atypical carcinoid and adenocarcinoma. The targeted next-generation sequencing analysis covering single nucleotide variations, copy number variations, and transcript fusions in a total of 161 cancer genes of the two different tumor components shows a similar molecular profile of shared and private gene mutations. These findings suggest their monoclonal origin from a transformed stem/progenitor tumor cell, which acquires a divergent differentiation during its development and progression and accumulates novel, specific mutations.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.

Prediction of hereditary nonpolyposis colorectal cancer using mRNA MSH2 quantitative and the correlation with nonmodifiable factor

BACKGROUND

Hereditary non-polyposis colon cancer is a dominantly inherited syndrome of colorectal cancer (CRC), with heightened risk for younger population. Previous studies link its susceptibility to the DNA sequence polymorphism along with Amsterdam and Bethesda criteria. However, those fail in term of applicability.

AIM

To determine a clear cut-off of MSH2 gene expression for CRC heredity grouping factor. Further, the study also aims to examine the association of risk factors to the CRC heredity.

METHODS

The cross-sectional study observed 71 respondents from May 2018 to December 2019 in determining the CRC hereditary status through MSH2 mRNA expression using reverse transcription-polymerase chain reaction and the disease's risk factors. Data were analyzed through Chi-Square, Fischer exact, t-test, Mann-Whitney, and multiple logistics.

RESULTS

There are significant differences of MSH2 within CRC group among tissue and blood; yet, negative for significance between groups. Through the blood gene expression fifth percentile, the hereditary CRC cut-off is 11059 fc, dividing the 40 CRC respondents to 32.5% with hereditary CRC. Significant risk factors include age, family history, and staging. Nonetheless, after multivariate control, age is just a confounder. Further, the study develops a probability equation with area under the curve 82.2%.

CONCLUSION

Numerous factors have significant relations to heredity of CRC patients. However, true important factors are staging and family history, while age and others are confounders. The study also established a definite cut-off point for heredity CRC based on mRNA MSH2 expression, 11059 fc. These findings shall act as concrete foundations on further risk factors and/or genetical CRC future studies.

Mixed adenoneuroendocrine carcinoma (MANEC) of the lower gastrointestinal tract: A systematic review with Bayesian hierarchical survival analysis

BACKGROUND

Mixed adeno-neuroendocrine carcinomas (MANEC) are a subgroup of mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) described as mixed neoplasms containing dual neuroendocrine and non-neuroendocrine components. The aim of this study was to appraise the prevalence of MANEC in the lower gastrointestinal (GI) tract and provide reliable estimates of survival.

METHOD

A systematic review was undertaken in accordance with PRISMA guidelines using PubMed, Embase, Cochrane Library of Systematic Review, Web of Science, and Scopus databases, and a Bayesian hierarchical survival pooled analysis was performed.

RESULTS

Of 182 unique records identified, 71 studies reporting on 752 patients met the inclusion criteria. Mean age was 64.2 ± 13.6, with a male-to-female ratio of 1.25. Overall, 60.3% of MANEC were located in the appendix, 29.3% in the colon, and 10.4% in the anorectum. More than a quarter (29%) of patients had stage IV disease at diagnosis, with higher prevalence in appendiceal than colonic and anorectal primaries. More than 80% had a high-grade (G3) endocrine component. Of the 152 patients followed up for a median of 20 months (interquartile range limits, 16.5-32), median overall survival was 12.3 months (95% credible interval [95%CrI], 11.3-13.7), with a 1.12 [95%CrI, 0.67-1.83] age-adjusted hazard ratio between metastatic and non-metastatic MANEC. Stage IV disease at diagnosis was more prognostically unfavorable in cases of colonic compared to anorectal origin.

CONCLUSION

MANEC is a clinically aggressive pathological entity. The results of this study provide new insights for the understanding of tumor location within the lower GI tract and its prognosis in terms of overall survival.

Gastroenteropancreatic neuroendocrine neoplasms G3: Novel insights and unmet needs

According to the 2019 WHO pathology grading system, high-grade gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) can be divided into well differentiated neuroendocrine tumors G3 (NETs G3) and poorly differentiated neuroendocrine carcinomas (NECs). GEP-NETs G3 and GEP-NECs present significant differences in driver genes and disease origin. NETs G3 and NECs have been confirmed to be two distinct diseases with different genetic backgrounds, however, this issue remains controversial. The prognosis of NETs G3 is significantly better than that of NECs. The differential diagnosis of GEP-NETs G3 and GEP-NECs should be combined with the patient's medical history, tumor histopathology, Ki-67 index, DAXX/ATRX, TP53 and Rb expression as well as other immunohistochemical indicators. In addition, the treatment strategies of these two subgroups are very different. Here, we summarize recent findings focused on the genomics, clinical manifestations, diagnosis, treatment and other aspects of high-grade GEP-NENs (G3). This review may help further our understanding of the carcinogenesis, diagnosis and treatment of GEP-NENs G3.

Neuroendocrine neoplasms of the pancreas: diagnosis and pitfalls

Common to neuroendocrine neoplasms of the pancreas is their expression of synaptophysin, chromogranin A, and/or INSM1. They differ, however, in their histological differentiation and molecular profile. Three groups can be distinguished: well-differentiated neuroendocrine neoplasms (neuroendocrine tumors), poorly differentiated neuroendocrine neoplasms (neuroendocrine carcinomas), and mixed neuroendocrine-non-neuroendocrine neoplasms. However, the expression of synaptophysin and, to a lesser extent, also chromogranin A is not restricted to the neuroendocrine neoplasms, but may also be in a subset of non-neuroendocrine epithelial and non-epithelial neoplasms. This review provides the essential criteria for the diagnosis of pancreatic neuroendocrine neoplasms including diagnostic clues for the distinction of high-grade neuroendocrine tumors from neuroendocrine carcinomas and an algorithm avoiding diagnostic pitfalls in the delineation of non-neuroendocrine neoplasms with neuroendocrine features from pancreatic neuroendocrine neoplasms.

Neuroendocrine Differentiation in Conventional Colorectal Adenocarcinomas: Incidental Finding or Prognostic Biomarker?

Simple Summary

Colorectal MANECs are highly aggressive carcinomas defined by a distinct neuroendocrine morphology and positivity for synaptophysin in the neuroendocrine component. It is unclear whether a neuroendocrine differentiation in conventional adenocarcinomas without a suggestive morphology is of clinical relevance. We tested 1002 conventional colorectal carcinomas with a non-neuroendocrine morphology for synaptophysin expression and correlated the results with clinicopathological characteristics as well as patient survival and compared the survival characteristics of synaptophysin expression groups to those of true MANECs. We found no survival differences between synaptophysin expression groups within conventional colorectal adenocarcinomas. MANECs, on the other hand, showed significantly worse survival characteristics. Our data suggest that synaptophysin expression in conventional colorectal adenocarcinomas is of minor prognostic relevance and that conventional adenocarcinomas with a diffuse synaptophysin expression should not be classified as MANECs.

Abstract

Background: Colorectal mixed adenoneuroendocrine carcinomas (MANECs) are clinically highly aggressive neoplasms. MANECs are composed of variable adenocarcinoma components combined with morphologically distinct neuroendocrine carcinoma components, which are confirmed by synaptophysin immunohistochemistry, the gold standard marker of a neuroendocrine differentiation. However, the biological behavior of adenocarcinomas that express synaptophysin but do not show a typical neuroendocrine morphology remains unclear. Methods: We investigated synaptophysin expression in 1002 conventional colorectal adenocarcinomas and correlated the results with clinicopathological characteristics and patient survival and compared the survival characteristics of synaptophysin expression groups to MANECs. Results: Synaptophysin expression in conventional colorectal adenocarcinomas was associated with a shortened disease-free survival (p = 0.037), but not with overall survival or disease-specific survival (DSS) in univariate analyses and without any survival impact in multivariate analyses. Patients with “true” MANECs, on the other hand, showed a significantly shorter survival than all conventional adenocarcinomas with or without synaptophysin expression in uni- and multivariate analyses (e.g., multivariate DSS: p < 0.001, HR: 5.20). Conclusions: Our study demonstrates that synaptophysin expression in conventional colorectal adenocarcinomas, in contrast to MANECs, is not associated with a significantly poorer clinical outcome when compared to adenocarcinomas without synaptophysin expression. Furthermore, our data suggest that conventional adenocarcinomas with a diffuse synaptophysin expression should not be classified as MANECs, also strongly arguing that synaptophysin testing should be reserved for carcinomas with an H&E morphology suggestive of a neuroendocrine differentiation.

Poorly differentiated neuroendocrine carcinomas of the gastrointestinal tract: A single-institute study of 43 cases

OBJECTIVES

To characterize the clinicopathologic and immunohistochemical features of poorly differentiated neuroendocrine carcinomas (NEC) in the gastrointestinal tract.

DESIGN

A total of 43 cases were identified and reassessed based on modern classification.

RESULTS

The cohort (27M, 16F; median age: 66 years) included 16 (37%) large cell NEC, 12 (28%) small cell NEC, 5 (12%) NEC not otherwise specified, and 10 (23%) mixed adenoneuroendocrine carcinomas. Tumor predominantly involved the colon (n = 14, 33%), rectum (n = 13, 30%), and esophagus (n = 9, 21%). Immunohistochemically, INSM1 was the most sensitive marker for neuroendocrine differentiation (28/28, 100%), followed by synaptophysin (40/43, 93%), CD56 (22/35, 63%), and chromogranin (18/40, 45%). SATB2, CDX2, CK20, CK7, abnormal p53, and PD-L1 was positive in 21/26 (81%), 26/37 (70%), 11/35 (31%), 10/35 (29%), 19/24 (79%), and 12/23 (52%) cases, respectively. Three of 25 (11%) were mismatch repair protein deficient. Of 21 resected tumors, 19 (90%) were ≥ pT3 and 13 (62%) had nodal metastasis. Twenty-eight (65%) had distant metastasis. The 5-year survival rate was 21%. The prognosis was stage dependent (p < 0.05), but not associated with tumor type, location, or specific immunomarkers.

CONCLUSION

Gastrointestinal NECs are aggressive neoplasms. INSM1, synaptophysin, and SATB2 are sensitive markers, although not site or tumor type specific.

Pituitary neuroendocrine tumors: a model for neuroendocrine tumor classification

The classification of adenohypophysial neoplasms as "pituitary neuroendocrine tumors" (PitNETs) was proposed in 2017 to reflect their characteristics as epithelial neuroendocrine neoplasms with a spectrum of clinical behaviors ranging from small indolent lesions to large, locally invasive, unresectable tumors. Tumor growth and hormone hypersecretion cause significant morbidity and mortality in a subset of patients. The proposal was endorsed by a WHO working group that sought to provide a unified approach to neuroendocrine neoplasia in all body sites. We review the features that are characteristic of neuroendocrine cells, the epidemiology and prognosis of these tumors, as well as further refinements in terms used for other pituitary tumors to ensure consistency with the WHO framework. The intense study of PitNETs has provided information about the importance of cellular differentiation in tumor prognosis as a model for neuroendocrine tumors in different locations.