Molecular characteristics of colorectal neuroendocrine carcinoma; similarities with adenocarcinoma rather than neuroendocrine tumor

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.

Potent molecular-targeted therapies for gastro-entero-pancreatic neuroendocrine carcinoma

Neuroendocrine neoplasms (NENs), which are characterized by neuroendocrine differentiation, can arise in various organs. NENs have been divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on morphological differentiation, each of which has a distinct etiology, molecular profile, and clinicopathological features. While the majority of NECs originate in the pulmonary organs, extrapulmonary NECs occur most predominantly in the gastro-entero-pancreatic (GEP) system. Although platinum-based chemotherapy is the main therapeutic option for recurrent or metastatic GEP-NEC patients, the clinical benefits are limited and associated with a poor prognosis, indicating the clinically urgent need for effective therapeutic agents. The clinical development of molecular-targeted therapies has been hampered due to the rarity of GEP-NECs and the paucity of knowledge on their biology. In this review, we summarize the biology, current treatments, and molecular profiles of GEP-NECs based on the findings of pivotal comprehensive molecular analyses; we also highlight potent therapeutic targets for future precision medicine based on the most recent results of clinical trials.

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.

Gallbladder neuroendocrine carcinoma: A report of two cases and literature review

Gallbladder neuroendocrine carcinoma (GB-NEC) is a rare, aggressive neuroendocrine carcinoma that arises from the gallbladder. Patients with GB-NEC usually have a poor prognosis. The present study described two cases diagnosed with GB-NEC and reviewed the literature to improve knowledge of GB-NEC. The present study reported on two cases of GB-NEC in male patients aged 65 and 66 years, respectively. Both patients underwent surgical resection. Postoperative pathology confirmed that one case had mixed adeno-neuroendocrine carcinoma and the other had large cell neuroendocrine carcinoma. In addition, both patients had uneventful recoveries following surgery and received cisplatin-etoposide combination chemotherapy. The present study summarized the two cases and reviewed the literature to improve understanding of GB-NEC. The results revealed that radiological findings of GB-NEC are non-specific. The present study demonstrated that surgical resection was still the most effective therapy and that postoperative adjuvant chemotherapy could markedly improve the prognosis of patients with GB-NEC.

Comparison of Metastatic Patterns Among Neuroendocrine Tumors, Neuroendocrine Carcinomas, and Nonneuroendocrine Carcinomas of Various Primary Organs

BACKGROUND

Both neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) exhibit neuroendocrine differentiation and are classified as neuroendocrine neoplasms (NENs). NECs and nonneuroendocrine neoplasms (non-NENs), such as adenocarcinoma, have similar mutational profiles. The purpose of this study was to identify differences in metastatic patterns and to identify the key factor causing these differences by simultaneously comparing the metastatic patterns of NETs, NECs and non-NENs from various primary organs.

METHODS

We retrieved data for 4,223 patients with NENs and 41,637 patients with non-NENs arising at various primary sites from an institutional database and then compared NET, NEC, and non-NEN metastatic patterns.

RESULTS

NETs and NECs showed generally similar metastatic patterns. Most NEN patients had a higher liver organotrophic metastasis rate, lower lung organotrophic metastasis rate, and lower pleural/peritoneal organotrophic metastasis rate than non-NEN patients. Some differences were characteristics of specific organs. Some of these site-specific differences were not caused by NENs but by non-NENs, including a higher bone organotrophic metastasis rate for medullary thyroid carcinoma and a lower bone organotrophic metastasis rate for pulmonary NEN. Other differences were probably caused by NENs, including a higher bone organotrophic metastasis rate for colorectal NETs. Uterine cervical NEC showed unique patterns of metastasis compared to NEN from other sites.

CONCLUSION

Significant differences between the metastatic patterns of NENs and non-NENs were detected. The multigene program that causes neuroendocrine differentiation might be associated with organotropic metastasis.

Colorectal Cancer Metastases in the Liver Establish Immunosuppressive Spatial Networking between Tumor-Associated SPP1+ Macrophages and Fibroblasts

PURPOSE

The liver is the most frequent metastatic site for colorectal cancer. Its microenvironment is modified to provide a niche that is conducive for colorectal cancer cell growth. This study focused on characterizing the cellular changes in the metastatic colorectal cancer (mCRC) liver tumor microenvironment (TME).

EXPERIMENTAL DESIGN

We analyzed a series of microsatellite stable (MSS) mCRCs to the liver, paired normal liver tissue, and peripheral blood mononuclear cells using single-cell RNA sequencing (scRNA-seq). We validated our findings using multiplexed spatial imaging and bulk gene expression with cell deconvolution.

RESULTS

We identified TME-specific SPP1-expressing macrophages with altered metabolism features, foam cell characteristics, and increased activity in extracellular matrix (ECM) organization. SPP1+ macrophages and fibroblasts expressed complementary ligand-receptor pairs with the potential to mutually influence their gene-expression programs. TME lacked dysfunctional CD8 T cells and contained regulatory T cells, indicative of immunosuppression. Spatial imaging validated these cell states in the TME. Moreover, TME macrophages and fibroblasts had close spatial proximity, which is a requirement for intercellular communication and networking. In an independent cohort of mCRCs in the liver, we confirmed the presence of SPP1+ macrophages and fibroblasts using gene-expression data. An increased proportion of TME fibroblasts was associated with the worst prognosis in these patients.

CONCLUSIONS

We demonstrated that mCRC in the liver is characterized by transcriptional alterations of macrophages in the TME. Intercellular networking between macrophages and fibroblasts supports colorectal cancer growth in the immunosuppressed metastatic niche in the liver. These features can be used to target immune-checkpoint-resistant MSS tumors.

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.

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.

Second-line treatment and prognostic factors in neuroendocrine carcinoma: the RBNEC study

Neuroendocrine carcinomas (NEC) are aggressive malignant diseases. Etoposide-based rechallenge (EBR) and the prognostic role of RB transcriptional corepressor 1 (RB1) status in second-line chemotherapy (2L) have not been studied. The objectives of this study were to report the results of 2L including EBR as well as prognostic factors in a national retrospective multicentre study. NEC patients treated with 2L and further, with tissue samples available, were included. RB1 status and morphological classification were reviewed centrally. Among the 121 NEC patients (40% female, median age 61 years) included, there were 73 small-cell NEC (60%), 34 large-cell NEC (28%) and 14 NEC (not otherwise specified, 12%). Primary sites were lung (39%), gastroenteropancreatic (36%), other (13%) and unknown (12%). Median Ki-67 index was 80%. Median progression-free survival (PFS) and overall survival (OS) under 2L were 2.1 and 6.2 months, respectively. No difference was observed between patients who received an 'adenocarcinoma-like' or a 'neuroendocrine-like' 2L or according to the RB1 status. Thoracic NEC primary was the only adverse prognostic factor for OS. EBR, administered to 31 patients, resulted in a 62% disease control rate with a median PFS and OS of 3.2 and 11.7 months, respectively. In the 94 patients with a relapse-free interval of ≥3 months after first-line platinum-etoposide chemotherapy, the median OS was 12 months in patients who received EBR as compared to 5.9 months in patients who did not (P = 0.043). EBR could be the best 2L option for patient with initial response to first-line platinum-etoposide lasting at least 3 months. RB1 status does not provide prognostic information in this setting.

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.

Expanding Therapeutic Opportunities for Extrapulmonary Neuroendocrine Carcinoma

Poorly differentiated neuroendocrine carcinomas (PD-NEC) are rare cancers garnering interest as they become more commonly encountered in the clinic. This is due to improved diagnostic methods and the increasingly observed phenomenon of "NE lineage plasticity," whereby nonneuroendocrine (non-NE) epithelial cancers transition to aggressive NE phenotypes after targeted treatment. Effective treatment options for patients with PD-NEC are challenging for several reasons. This includes a lack of targetable, recurrent molecular drivers, a paucity of patient-relevant preclinical models to study biology and test novel therapeutics, and the absence of validated biomarkers to guide clinical management. Although advances have been made pertaining to molecular subtyping of small cell lung cancer (SCLC), a PD-NEC of lung origin, extrapulmonary (EP)-PD-NECs remain understudied. This review will address emerging SCLC-like, same-organ non-NE cancer-like and tumor-type-agnostic biological vulnerabilities of EP-PD-NECs, with the potential for therapeutic exploitation. The hypotheses surrounding the origin of these cancers and how "NE lineage plasticity" can be leveraged for therapeutic purposes are discussed. SCLC is herein proposed as a paradigm for supporting progress toward precision medicine in EP-PD-NECs. The aim of this review is to provide a thorough portrait of the current knowledge of EP-PD-NEC biology, with a view to informing new avenues for research and future therapeutic opportunities in these cancers of unmet need.

Nuclear survivin is a prognosticator in gastroenteropancreatic neuroendocrine neoplasms: a meta-analysis

Purpose

Gastroenteropancreatic neuroendocrine neosplasms (GEP-NEN) are biologically heterogenous tumors with an increasing incidence over the past decades. Although efforts have been made in the treatment of these tumors, survival rates in metastasized tumor stages remain frustrating. Thus, there is an urgent need to identify novel targets as alternative treatment options. In this regard, the inhibitor of apoptosis protein (IAP) family member survivin could be such an attractive target. Therefore, aim of our meta-analysis was to assess the role of survivin as a biomarker and predictor in GEP-NEN.

Methods

Medline, Web of Science and Scopus were screened for studies that fulfilled our selection criteria. Quality assessement of the studies was based on design, methodology, generalizability and results analysis. Meta-analyses were conducted using a random-effects model and effect size measures were expressed as pooled Hazard Ratio (HR) or Odds Ratio (OR) with 95% Confidence Interval (CI).

Results

Six eligible studies with 649 patients (range 77–132) assessed survivin expression in GEP-NEN by immunohistochemistry. High expression levels of nuclear survivin in GEP-NEN correlated with a shorter overall survival (HR 3.10; 95% CI 2.15–4.47; p < 0.0001). In contrast to cytoplasmic survivin (OR 1.24; CI 0.59–2.57; p = 0.57), nuclear survivin was also associated (OR 15.23; CI 3.61–64.23; p = 0.0002) with G3/poorly differentiated GEP-NEN.

Conclusion

Nuclear Survivin is highly expressed in more aggressive G3 GEP-NEN and correlates with a poor outcome. Survivin is therefore an interesting molecule for a targeted therapy, especially for patients with highly proliferative G3 GEP-NENs.

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.

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.

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.

The molecular characteristics of high-grade gastroenteropancreatic neuroendocrine neoplasms

High-grade (HG) gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) are rare but have a very poor prognosis and represent a severely understudied class of tumours. Molecular data for HG GEP-NEN are limited, and treatment strategies for the carcinoma subgroup (HG GEP-NEC) are extrapolated from small-cell lung cancer (SCLC). After pathological re-evaluation, we analysed DNA from tumours and matched blood samples from 181 HG GEP-NEN patients; 152 neuroendocrine carcinomas (NEC) and 29 neuroendocrine tumours (NET G3). Based on the sequencing of 360 cancer-related genes, we assessed mutations and copy number alterations (CNA). For NEC, frequently mutated genes were TP53 (64%), APC (28%), KRAS (22%) and BRAF (20%). RB1 was only mutated in 14%, but CNAs affecting RB1 were seen in 34%. Other frequent copy number losses were ARID1A (35%), ESR1 (25%) and ATM (31%). Frequent amplifications/gains were found in MYC (51%) and KDM5A (45%). While these molecular features had limited similarities with SCLC, we found potentially targetable alterations in 66% of the NEC samples. Mutations and CNA varied according to primary tumour site with BRAF mutations mainly seen in colon (49%), and FBXW7 mutations mainly seen in rectal cancers (25%). Eight out of 152 (5.3%) NEC were microsatellite instable (MSI). NET G3 had frequent mutations in MEN1 (21%), ATRX (17%), DAXX, SETD2 and TP53 (each 14%). We show molecular differences in HG GEP-NEN, related to morphological differentiation and site of origin. Limited similarities to SCLC and a high fraction of targetable alterations indicate a high potential for better-personalized treatments.

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 Carcinomas of the Digestive Tract: What Is New?

Neuroendocrine carcinomas (NEC) are rare tumors with a rising incidence. They show poorly differentiated morphology with a high proliferation rate (Ki-67 index). They frequently arise in the lung (small and large-cell lung cancer) but rarely from the gastrointestinal tract. Due to their rarity, very little is known about digestive NEC and few studies have been conducted. Therefore, most of therapeutic recommendations are issued from work on small-cell lung cancers (SCLC). Recent improvement in pathology and imaging has allowed for better detection and classification of high-grade NEN. The 2019 World Health Organization (WHO) classification has described a new entity of well-differentiated grade 3 neuroendocrine tumors (NET G-3), with better prognosis, that should be managed separately from NEC. NEC are aggressive neoplasms often diagnosed at a metastatic state. In the localized setting, surgery can be performed in selected patients followed by adjuvant platinum-based chemotherapy. Concurrent chemoradiotherapy is also an option for NEC of the lung, rectum, and esophagus. In metastatic NEC, chemotherapy is administered with a classic combination of platinum salts and etoposide in the first-line setting. Peptide receptor radionuclide therapy (PRRT) has shown positive results in high-grade NEN populations and immunotherapy trials are still ongoing. Available therapies have improved the overall survival of NEC but there is still an urgent need for improvement. This narrative review sums up the current data on digestive NEC while exploring future directions for their management.

Prognostic factors of metastatic neuroendocrine carcinoma under first-line treatment with platinum etoposide with a focus on NEC score and Rb expression: Results from the multicentre RBNEC study of the Groupe d'Etude des Tumeurs Endocrines (GTE) and the ENDOCAN-RENATEN network

INTRODUCTION AND AIM

Neuroendocrine carcinomas (NECs) are aggressive malignant diseases. Platinum-etoposide (PE) combination is the standard first-line treatment, whatever the primary location. The NEC score and also retinoblastoma protein (Rb) status have been suggested to be predictive/prognostic factors in NEC. The primary objective of our multicentric retrospective study was to evaluate the prognostic relevance of the NEC score and Rb status, assessed by immunohistochemistry in PE-treated patients with metastatic NEC.

METHODS

Seven centres participated. The inclusion criteria were NEC, whatever the primary site, metastatic stage, first-line treatment with PE and tissue samples available. Rb status was determined centrally.

RESULTS

We report multicentric data from 185 metastatic patients (37% women, median age 63). There were 108 small-cell NECs (SCNECs, 58.4%), 50 large-cell NECs (LCNECs, 27%) and 27 not otherwise specified NECs (nosNECs, 14.6%). The primary sites were the thorax (37%), gastroenteropancreatic sites (38%), unknown (15%) and other (9%). The mean Ki-67 index was 76% (range 20-100). Rb status was interpretable in 122 cases. Rb expression was lost in 74% of the cases: 84% of SCNEC vs. 60% and 63% of LCNEC and nosNEC, respectively (p = 0.016). Objective response was seen in 70% of SCNEC, 45% of LCNEC and 48% of nosNEC (p < 0.001) and in 62% of Rb-negative tumours vs. 46% of Rb-positive tumours (p = 0.3). There was no difference in median progression-free survival or overall survival (OS) as per Rb status. Age, NEC score and response to chemotherapy were the main factors associated with OS in our cohort.

CONCLUSION

In our series, Rb status had no prognostic impact in PE-treated metastatic patients with NEC, whereas age, NEC score and response to chemotherapy were the main factors associated with OS.

Clinicopathological and molecular characteristics of endometrial neuroendocrine carcinomas reveal preexisting endometrial carcinoma origin

Endometrial neuroendocrine carcinoma is a rare disease with unknown clinicopathological and molecular characteristics. Therefore, we conducted the present study to elucidate the clinicopathological and molecular characteristics of endometrial neuroendocrine carcinoma, as compared to conventional endometrial carcinoma, and to determine the origin of the former. We analyzed 22 endometrial neuroendocrine carcinomas and 22 conventional endometrial neoplasia cases with respect to clinical, histological and genetic features. Of these, 21/22 neuroendocrine carcinoma cases were admixed carcinomas, with 15 admixed with endometrioid adenocarcinoma. Genetic analysis of hotspot mutations in 50 cancer-related genes revealed that the neuroendocrine carcinoma group carried mutations in PIK3CA (12/22 cases; 54%) and PTEN (8/22 cases; 36%), commonly encountered in endometrioid adenocarcinoma. Comparative statistical analysis of neuroendocrine carcinoma and conventional endometrial neoplasia cases showed a significant trend only in PIK3CA mutation. Moreover, in six mixed-type neuroendocrine carcinoma cases, macrodissection was used to separate the neuroendocrine carcinoma and endometrioid adenocarcinoma components for next-generation sequencing, which revealed several mutations common among the two. These findings suggest that endometrial neuroendocrine carcinoma could originate from conventional endometrial neoplasia, especially endometrioid adenocarcinoma.

Comprehensive analysis of mutational and clinicopathologic characteristics of poorly differentiated colorectal neuroendocrine carcinomas

Poorly differentiated neuroendocrine carcinoma (NEC) is a rare subtype of colorectal cancer (CRC). This study aimed to investigate clinicopathologic characteristics of colorectal NECs and elucidate genomic differences and similarities between colorectal NECs and colorectal adenocarcinomas (ACs). A total of 30 colorectal NECs were screened for frequently identified CRC oncogenic driver genes by targeted next-generation sequencing of 382 genes. The median age of the patients was 67 years (range, 44 to 88 years). NECs occurred predominantly in the rectum (47%) and exhibited multiple adverse prognostic pathologic factors, including frequent lymphatic and vascular invasions, high rates of lymph node metastasis and distant metastasis and advanced TNM stage. The 1-, 3-, and 5-year overall survival rates of NEC patients were 46.7%, 36.4%, and 32.7%, respectively, with a median overall survival period of 11.5 months. In a molecular analysis, NECs showed high rates of BRAF mutation (23%), predominantly p.V600E (71%), and alterations in RB1 (47%), particularly deletion (57%). The frequencies and distributions of other genes, such as KRAS, APC, SMAD4, and PIK3CA, and microsatellite instability status were similar to those of ACs. These findings provide beneficial information for selecting therapeutic options, including targeted therapy, and a better understanding of the histogenesis of this tumour.

Genomics of High-Grade Neuroendocrine Neoplasms: Well-Differentiated Neuroendocrine Tumor with High-Grade Features (G3 NET) and Neuroendocrine Carcinomas (NEC) of Various Anatomic Sites

High-grade neuroendocrine neoplasms (HG-NENs) are clinically aggressive diseases, the classification of which has recently been redefined. They now include both poorly differentiated NENs (neuroendocrine carcinoma, NECs) and high proliferating well-differentiated NENs (called grade 3 neuroendocrine tumors, G3 NETs, in the digestive system). In the last decade, the "molecular revolution" that has affected all fields of medical oncology has also shed light in the understanding of HG NENs heterogeneity and has provided new diagnostic and therapeutic tools, useful in the management of these malignancies. Considering the kaleidoscopic aspects of HG NENs in various anatomical sites, this review systematically addresses the genomic landscape of such neoplasm throughout the more common thoracic and digestive locations, as well as it will consider other rare but not exceptional primary sites, including the skin, the head and neck, and the urogenital system. The revision of the available literature will then be oriented to understand the translational relevance of molecular data, by analyzing conceptual issues, clinicopathological correlations, and unmet needs in this field.

Molecular Pathology of Well-Differentiated Gastro-entero-pancreatic Neuroendocrine Tumors

Well differentiated neuroendocrine tumors (NETs) arising in the gastrointestinal and pancreaticobiliary system are the most common neuroendocrine neoplasms. Studies of the molecular basis of these lesions have identified genetic mutations that predispose to familial endocrine neoplasia syndromes and occur both as germline events and in sporadic tumors. The mutations often involve epigenetic regulators rather than the oncogenes and tumor suppressors that are affected in other malignancies. Somatic copy number alterations and miRNAs have also been implicated in the development and progression of some of these tumors. The molecular profiles differ by location, but many are shared by tumors in other sites, including those outside the gastroenteropancreatic system. The approach to therapy relies on both the neuroendocrine nature of these tumors and the identification of specific alterations that can serve as targets for precision oncologic approaches.

Biomarkers of Response to Etoposide-Platinum Chemotherapy in Patients with Grade 3 Neuroendocrine Neoplasms

Etoposide-platinum (EP) chemotherapy has long been the reference treatment for grade 3 neuroendocrine neoplasms (G3 NEN). However, G3 NEN are heterogeneous, including well-differentiated tumors (NET) and poorly differentiated large (LCNEC) or small (SCNEC) cell carcinomas, whose response to EP chemotherapy varies considerably. Our aim was to evaluate predictive biomarkers for the response to EP chemotherapy in G3 NEN. We retrospectively studied 89 patients with lung (42%) and digestive (58%) G3 NEN treated by EP chemotherapy between 2006 and 2020. All cases were centrally reviewed for cytomorphology/Ki-67 and immunohistochemistry of retinoblastoma protein (Rb)/p53/p16, analyzed using a semi-quantitative score. The absence of Rb staining (Rbinap) or the absence of very intense p53 staining (p53inap) were considered inappropriate. Rb staining was also studied as a quantitative marker, the best threshold being determined by ROC curve. Intense p16 staining (p16high) also suggested cell cycle dysregulation. Our primary endpoint was the objective response rate (ORR). We included 10 G3 NET, 31 LCNEC and 48 SCNEC, which showed ORR of 20%, 32% and 75%, respectively (NET vs. NEC, p = 0.040; LCNEC vs. SCNEC, p < 0.001). The ORR was significantly higher in NEN presenting with Rbinap (63% vs. 42%, p = 0.025) and p16high (66% vs. 35%, p = 0.006). Rb < 150 optimally identified responders (AUC = 0.657, p < 0.001). The ORR was 67% in Rb < 150 (vs. 25%, p = 0.005). On multivariate analysis, only Rb < 150 was independently associated with ORR (OR 4.16, 95% CI 1.11-15.53, p = 0.034). We confirm the heterogeneity of the response to EP treatment in G3 NEN. Rb < 150 was the best predictive biomarker for the response to EP, and p53 immunostaining had no additional value.

ctDNA in Neuroendocrine Carcinoma of Gastroenteropancreatic Origin or of Unknown Primary: The CIRCAN-NEC Pilot Study

INTRODUCTION

Gastroenteropancreatic neuroendocrine carcinomas (GEPNEC) are characterized by a heterogeneous molecular profile and a poor prognosis. Circulating tumour DNA (ctDNA) analysis may be useful for NEC management. This study aimed at describing ctDNA mutations, to assess their predictive value for response to chemotherapies, and their change according to disease progression.

METHODS

The CIRCAN-NEC study included patients with GEPNEC or NEC from an unknown primary, scheduled to begin first- or second-line chemotherapy. Blood samples were collected prior to chemotherapy initiation, at first evaluation, and during disease progression. ctDNA was sequenced by next-generation sequencing (NGS). Molecular response was defined as a decrease of at least 30% of the mutant allele fraction.

RESULTS

All 24 patients included received platinum-etoposide first-line chemotherapy; 19 received a FOLFIRI-based post-first-line regimen. Twenty-two patients had at least one driver mutation: TP53 (n = 21), RB1 (n = 2), KRAS (n = 4), and BRAF (n = 3). Ten (42%) had an "adenocarcinoma-like" profile. Five of 6 patients with matching ctDNA/tissue NGS harboured at least one concordant mutation (44% concordance at the gene level). The concordance rate between ctDNA mutation/immunohistochemistry profile was 64% (7/11) for TP53/p53+ and 14% (1/7) for RB1/pRb-. In this pilot study including few patients by subgroups, patients with KRAS (HR = 3.60, 95% CI [1.06-12.04]) and BRAF (HR = 4.25, 95% CI [1.11-16.40]) mutations had shorter progression-free survival (PFS) under platinum-etoposide, while the 2 patients with RB1 mutations had shorter PFS under FOLFIRI-based chemotherapy. Twenty-eight periods of treatment were assessed: 10 patients had a molecular response (7/10 had a morphological response), which was associated with longer PFS (HR = 0.37, 95% CI [0.15; 0.91]).

CONCLUSION

This pilot study shows a high sensitivity of ctDNA assessment, which is encouraging for the future management of GEPNEC (tumour molecular diagnosis and evaluation of disease progression).

Patient-Derived Organoid Models of Human Neuroendocrine Carcinoma

Gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) is a poorly understood disease with limited treatment options. A better understanding of this disease would greatly benefit from the availability of representative preclinical models. Here, we present the potential of tumor organoids, three-dimensional cultures of tumor cells, to model GEP-NEC. We established three GEP-NEC organoid lines, originating from the stomach and colon, and characterized them using DNA sequencing and immunohistochemistry. Organoids largely resembled the original tumor in expression of synaptophysin, chromogranin and Ki-67. Models derived from tumors containing both neuroendocrine and non-neuroendocrine components were at risk of overgrowth by non-neuroendocrine tumor cells. Organoids were derived from patients treated with cisplatin and everolimus and for the three patients studied, organoid chemosensitivity paralleled clinical response. We demonstrate the feasibility of establishing NEC organoid lines and their potential applications. Organoid culture has the potential to greatly extend the repertoire of preclinical models for GEP-NEC, supporting drug development for this difficult-to-treat tumor type.

Neuroendocrine Carcinomas of the Gallbladder: A Clinicopathologic and Immunohistochemical Analysis of 34 Resected Cases

Neuroendocrine carcinoma (NEC) is an aggressive malignant tumor that rarely arises from the gallbladder. Here, we investigated the clinicopathologic and immunohistochemical characteristics of 34 NECs of the gallbladder. The patients were predominantly women (68%) with a median age of 63 years (range, 37 to 82 y). NECs frequently occurred in the fundus (44%) as mass-forming lesions (66%). Histologically, 17 tumors were of small cell type, and another 17 were of large cell type. Twenty-three cases (68%) were associated with biliary intraepithelial neoplasia (38%) and intracholecystic papillary neoplasm (29%). The majority of tumors exhibited a diffuse growth pattern (74%), followed by organoid (24%) or scirrhous (2%) growth patterns. Histologic features related to neuroendocrine differentiation, such as nuclear molding (56%), perilobular pseudopalisading (18%), and rosette formation (15%), were identified. Immunohistochemically, cytokeratin 7 and 20 were expressed in 19 (56%) and 8 (24%) cases, respectively. Loss of Rb1 expression and concomitant overexpression of p16 were observed in 25 (74%) cases. No BRAF mutations were identified in any of the 34 NECs. For survival analysis, the 1-, 3-, and 5-year overall survival rates were 64%, 35%, and 19%, respectively. In a multivariate analysis, the receipt of adjuvant chemoradiation therapy was identified as the only independent prognostic factor associated with the overall survival rate. The 1- and 3-year overall survival rates of patients with NECs were poorer for patients with poorly differentiated adenocarcinoma of the gallbladder (P<0.001). The complete resection and application of postoperative adjuvant therapy may influence a better clinical outcome in patients with NEC of the gallbladder.

Clinical and Translational Research Challenges in Neuroendocrine Tumours

Neuroendocrine tumours (NETs) represent a range of neoplasms that may arise from any (neuro)endocrine cell situated in any part of the human body. As any other rare diseases, NETs face several difficulties in relation to research. This review will describe some of the main challenges and proposed solutions faced by researchers with expertise in rare malignancies. Some of the most common challenges in clinical and translational research are enumerated in this review, covering aspects from clinical, translational and basic research. NETs being a heterogeneous group of diseases and a limited sample size of clinical and translational research projects are the main challenges. Challenges with NETs lay over the disparities between healthcare models to tackle rare diseases. NETs add an extra layer of complexity due to a numerous group of different entities. Prospective real-world data trials are an opportunity for rare cancers with the revolution of electronic health technologies. This review explores potential solutions to these challenges that could be useful not only to the NET community but also to other rare tumours researchers.

Should immunohistochemical expression of mismatch repair (MMR) proteins and microsatellite instability (MSI) analysis be routinely performed for poorly differentiated colorectal neuroendocrine carcinomas?

SUMMARY

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) are typically associated with poor outcomes. The mechanisms of their aggressiveness are still being investigated. Microsatellite instability (MSI) has recently been found in colorectal NECs showing aberrant methylation of the MLH1 gene and is associated with improved prognosis. We present a 76-year-old lady with an ascending colon tumour showing features of a pT3 N0 R0, large cell NEC (LCNEC) following right hemicolectomy. The adjacent mucosa showed a sessile serrated lesion (SSL) with low-grade dysplasia. Immunohistochemistry showed loss of expression for MLH1 and PMS2 in both the LCNEC and dysplastic SSL. Molecular analysis indicated the sporadic nature of the MLH1 mismatch repair (MMR) protein-deficient status. Our patient did not receive adjuvant therapy and she is alive and disease-free after 34 months follow-up. This finding, similar to early-stage MMR-deficient colorectal adenocarcinoma, is likely practice-changing and will be critical in guiding the appropriate treatment pathway for these patients. We propose that testing of MMR status become routine for early-stage colorectal NECs.

LEARNING POINTS

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) are known to be aggressive and typically associated with poor outcomes. A subset of colorectal NECs can display microsatellite instability (MSI) with mismatch repair (MMR) protein-deficient status. MMR-deficient colorectal NECs have been found to have a better prognosis compared with MMR-proficient NECs. MMR status can be detected using immunohistochemistry. Immunohistochemistry for MMR status is routinely performed for colorectal adenocarcinomas. Immunohistochemical expression of MMR protein and MSI analysis should be performed routinely for early-stage colorectal NECs in order to identify a subgroup of MMR-deficient NECs which are associated with a significantly more favourable prognosis.

Neuroendocrine Tumors of the Gastrointestinal Tract and Pancreas

Neuroendocrine neoplasms (NENs) of the gastrointestinal (GI) tract and pancreas are a rare and heterogeneous group of neoplasms characterized by common cellular features as well as unique site-specific traits. GI and pancreatic NENs are much rarer than the more common adenocarcinomas arising at these sites. However, the incidences of GI and pancreatic NENs have increased significantly, particularly in the stomach and common site, followed by rectum, appendix, colon, and stomach. Pancreatic NENs are also uncommon, with fewer than 1 per 100,000, accounting for 1% to 2% of all pancreatic neoplasms.

Biomarkers for Pancreatic Neuroendocrine Neoplasms (PanNENs) Management-An Updated Review

Pancreatic neuroendocrine tumors (PanNENs) are rare sporadic cancers or develop as part of hereditary syndromes. PanNENs can be both functioning and non-functioning based on whether they produce bioactive peptides. Some PanNENs are well differentiated while others-poorly. Symptoms, thus, depend on both oncological and hormonal causes. PanNEN diagnosis and treatment benefit from and in some instances are guided by biomarker monitoring. However, plasmatic monoanalytes are only suggestive of PanNEN pathological status and their positivity is typically followed by deepen diagnostic analyses through imaging techniques. There is a strong need for new biomarkers and follow-up modalities aimed to improve the outcome of PanNEN patients. Liquid biopsy follow-up, i.e., sequential analysis on tumor biomarkers in body fluids offers a great potential, that need to be substantiated by additional studies focusing on the specific markers and the timing of the analyses. This review provides the most updated panorama on PanNEN biomarkers.

Whole genome sequencing of colorectal neuroendocrine tumors and in-depth mutational analyses

Colorectal neuroendocrine tumors (NETs) are rare neoplasms and studies on colorectal NETs are relatively few compared to other tumors. To better understand the pathogenesis of this tumor, we performed whole-genome sequencing and follow-up verification using Sanger sequencing of the colorectal NETs and paired para-tumor tissue. We analyzed the features of the gene mutation spectrum and mutation signature patterns, and analyzed the four pathways that were altered by gene mutation in pancreatic neuroendocrine tumors, including DNA damage and repair, chromatin remodeling, telomere maintenance and mTOR signaling activation. We found that PARP4 which is related to the DNA damage and repair pathway; TSC2, which is related to the mTOR signaling activation pathway; and SLX1A, which is related to telomere maintenance, were mutated in colorectal NETs. Our data analyzed characteristics of gene mutation in colorectal NETs at the whole-genome level, and may help to better understand the pathogenesis of colorectal NETs and may be helpful for potential tumor therapy in the future.

Neuroendocrine neoplasms of the breast: A review focused on the updated World Health Organization (WHO) 5th Edition morphologic classification

Neuroendocrine breast neoplasms are uncommon invasive carcinomas that have historically been poorly defined due to various definitions of what constitutes a neuroendocrine carcinoma. The 5th Edition of the World Health Organization (WHO) Classification of Breast Tumors has moved to a dichotomous classification of neuroendocrine neoplasms in the breast in order to become standardized with classifications of other organ systems. Neuroendocrine breast neoplasms in the new edition are classified as "neuroendocrine tumor" and "neuroendocrine carcinoma." Key changes are exclusion of special histologic types (solid papillary carcinoma and hypercellular variant of mucinous carcinoma) and the inclusion of large cell neuroendocrine carcinoma. Neuroendocrine tumors are genetically heterogenous and harbor molecular alterations that differ from invasive carcinoma, no special type. Neuroendocrine carcinomas (high-grade) show some overlapping molecular alterations with their counterparts in other organ systems. Data regarding the prognostic significance of neuroendocrine differentiation are conflicting, and histologic grade and tumor stage remain the main prognostic parameters. Current management of neuroendocrine neoplasms is not different from other types of breast carcinoma. This review will provide an update to the current WHO classification of neuroendocrine breast neoplasms and describe pertinent clinical, histologic, and molecular features of these uncommon tumors.

Gastroenteropancreatic High-Grade Neuroendocrine Neoplasms: Histology and Molecular Analysis, Two Sides of the Same Coin

BACKGROUND

In gastroenteropancreatic (GEP) high-grade neuroendocrine neoplasms (H-NENs), Ki-67 threshold of 55% defines three prognosis subclasses: neuroendocrine tumor (NET) G3, neuroendocrine carcinoma (NEC) <55%, and NEC ≥55%. We investigated whether the molecular profiling of H-NENs differs among these subcategories and evaluated potential therapeutic targets, including PD-L1.

METHODS

In GEP-NEN patients, we evaluated: (i) 55% threshold for Ki-67 labeling index for further stratifying NEC and (ii) immunoreactivity and gene mutations by immunohistochemistry and targeted next-generation sequencing (T-NGS).

RESULTS

Fifteen NETs G3 and 39 NECs were identified. Ki-67 labeling index was <55% in 9 NECs and ≥55% in 30 NECs. Gene mutations by NGS (TP53, 32.9%; KRAS, 5.5%; BRAF, 4.1%) were detected in 46.6% NENs, significantly enriched in NEC ≥55% (76.7%) compared to NEC <55% (55.6%) or NET (20.0%). PD-L1 staining in tumor-infiltrating lymphocytes was observed in NEC ≥55% (36.7%; p = 0.03). Median OS was 4.3 years in NET G3, 1.8 years in NEC <55%, and 0.7 years in NEC ≥55% (p <0.0001); it was 2.3 years with NGS wild-type, 0.7 years with ≥1 mutation (p <0.0001), 0.8 years in PD-L1-positive patients, and 1.7 years in PD-L1-negative subjects (p = 0.0004). In multivariate analysis, only the proposed subclassification approach yielded statistically significant differences between groups (NEC <55% vs. NET G3, HR 14.1, 95% CI 2.2-89.8, p = 0.005; NEC ≥55% vs. NET G3, HR 25.8, 95% CI 3.9-169, p = 0.0007).

CONCLUSIONS

These findings identify NEC ≥55% as a biologically and prognostically distinct subtype and pave the way for more personalized treatment.

Chemotherapy in Resected Neuroendocrine Carcinomas of the Digestive Tract: A National Study from the French Group of Endocrine Tumours

BACKGROUND

Neuroendocrine carcinomas (NECs) of the digestive tract are rare and aggressive tumours. In localised disease the treatment is surgery. Based on expert consensus, international guidelines recommend the administration of adjuvant chemotherapy combining etoposide and platinum derivatives, justified by the high risk of metastatic relapse. However, no clinical study has proven the benefit of neoadjuvant or adjuvant chemotherapy.

OBJECTIVES

We aimed to evaluate the effect of neoadjuvant +/- adjuvant and adjuvant therapy in this indication.

METHODS

We performed a retrospective observational French study to evaluate overall survival (OS) and disease-free survival (DFS), prognostic factors for survival, and chemotherapy toxicity.

RESULTS

Seventy-three patients had surgical resection of a localised digestive NEC between January 1, 2000 and December 31, 2016. The majority of patients presented colorectal (35%) tumours and the median Ki-67 value was 70%. Forty-three patients received chemotherapy, either perioperative (neoadjuvant +/- adjuvant) or adjuvant. The median OS and DFS for the whole population was 24 and 9 months, respectively. The median OS and DFS for patients receiving chemotherapy was 62 and 13 months, respectively. Positive postoperative node status and Ki-67 ≥80% had a negative prognostic impact on OS and DFS. Administration of chemotherapy had a positive prognostic impact on OS and DFS. Sixteen grade 3/4 toxicities were reported without toxic death.

CONCLUSIONS

Our results suggest a positive effect on survival of chemotherapy in resected digestive NECs, but further studies are needed to confirm these results.

An Open-Label, Single-Arm, Two-Stage, Multicenter, Phase II Study to Evaluate the Efficacy of TLC388 and Genomic Analysis for Poorly Differentiated Neuroendocrine Carcinomas

BACKGROUND

The discovery of effective therapeutic options for treating metastatic poorly differentiated neuroendocrine carcinoma (NEC) after prior platinum-based chemotherapy remains elusive. This study analyzed the efficacy of TLC388 (Lipotecan) Hydrochloride, a novel camptothecin analog, for pretreated patients with metastatic NEC.

METHODS

This single-arm, two-stage, phase II clinical trial was conducted at four community and academic centers in Taiwan. Patients aged 20 years or older with confirmed metastatic NEC and who had received prior systemic therapy with etoposide plus cisplatin were enrolled between July 2015 and May 2018. Patients received 40 mg/m² of TLC388 intravenously on days 1, 8, and 15 of a 28-day cycle until disease progression or unacceptable toxic effects. Gene mutations were analyzed by next-generation sequencing.

RESULTS

Twenty-three patients with a median age of 61 (range, 44-73) years, 18 of whom were men (78%), were enrolled. Patients received a median of 2 (range, 0-6) treatment cycles. Among 20 evaluable patients, 3 patients exhibited stable disease and no patient experienced a complete or partial remission, resulting in a disease control rate of 15%. Median progression-free survival was 1.8 (95% confidence interval [CI], 0.4-15) months, and the median overall survival was 4.3 (95% CI, 1.7-15) months. The most common treatment-related hematologic adverse events at grade 3 or higher were leukopenia (22.7%), anemia (31.8%), and thrombocytopenia (18.2%). The most frequent mutated genes in 35 patients with NEC were ARSA, DPYD, HEXB, BRCA1, HPD, MYBPC3, BBS2, IL7R, HSD17B4, and PRODH.

CONCLUSION

TLC388 demonstrates limited antitumor activity in metastatic NEC. ClinicalTrials.gov identifier: NCT02457273.

IMPLICATIONS FOR PRACTICE

Poorly differentiated neuroendocrine carcinomas (NECs) are rare and aggressive. Currently, effective therapeutic options for treating metastatic poorly differentiated NECs beyond platinum-based chemotherapy remain elusive. In this single-arm, multicenter, phase II study, 23 patients with NEC were enrolled and received TLC388 (Lipotecan) Hydrochloride, which is a novel camptothecin analog. The results demonstrated the disease control rate of 15%, the median progression-free survival of 1.8 (95% confidence interval [CI], 0.4-15) months, and the median overall survival of 4.3 (95% CI, 1.7-15) months. Most importantly, several novel genetic mutations and pathways were identified. These results offer the opportunity to develop future treatment strategies in this rare cancer.

Clinical applications of (epi)genetics in gastroenteropancreatic neuroendocrine neoplasms: Moving towards liquid biopsies

High-throughput analysis, including next-generation sequencing and microarrays, have strongly improved our understanding of cancer biology. However, genomic data on rare cancer types, such as neuroendocrine neoplasms, has been lagging behind. Neuroendocrine neoplasms (NENs) develop from endocrine cells spread throughout the body and are highly heterogeneous in biological behavior. In this challenging disease, there is an urgent need for new therapies and new diagnostic, prognostic, follow-up and predictive biomarkers to aid patient management. The last decade, molecular data on neuroendocrine neoplasms of the gastrointestinal tract and pancreas, termed gastroenteropancreatic NENs (GEP-NENs), has strongly expanded. The aim of this review is to give an overview of the recent advances on (epi)genetic level and highlight their clinical applications to address the current needs in GEP-NENs. We illustrate how molecular alterations can be and are being used as therapeutic targets, how mutations in DAXX/ATRX and copy number variations could be used as prognostic biomarkers, how far we are in identifying predictive biomarkers and how genetics can contribute to GEP-NEN classification. Finally, we discuss recent studies on liquid biopsies in the field of GEP-NENs and illustrate how liquid biopsies can play a role in patient management. In conclusion, molecular studies have suggested multiple potential biomarkers, but further validation is ongoing.

Adjuvant Chemotherapy Versus Observation Following Resection for Patients With Nonmetastatic Poorly Differentiated Colorectal Neuroendocrine Carcinomas

OBJECTIVE

The aim of this study was to determine whether adjuvant chemotherapy (AC) provides a survival benefit in patients with nonmetastatic poorly differentiated colorectal neuroendocrine carcinomas (CRNECs) following resection.

BACKGROUND

There is little evidence to support the association between use of AC and improved overall survival (OS) in patients with CRNECs.

METHODS

Patients with resected non-metastatic CRNECs were identified in the National Cancer Database (2004-2014). Inverse probability of treatment weighting (IPTW) method was used to reduce the selection bias. IPTW-adjusted Kaplan-Meier curves and Cox proportional hazards models were used to compare OS of patients in different treatment groups.

RESULTS

A total of 806 patients diagnosed between 2004 and 2014 met the study entry criteria. Of these, 394 patients (48.9%) received AC. IPTW-adjusted Kaplan-Meier curves showed that median OS was significantly longer for AC versus observation [57.4 (interquartile range, IQR, 14.8-153.8) vs 38.2 (IQR, 10.4-125.4) months; P = 0.007]. In IPTW-adjusted Cox proportional hazards regression analysis, AC was associated with a significant OS benefit [hazard ratio (HR) = 0.73, 95% confidence interval (CI) 0.64-0.84; P < 0.001]. The results were consistent across subgroups stratified by pathologic T stage, pathologic N stage, and surgical margin status. Subgroup analysis according to tumor location demonstrated improved OS in the adjuvant therapy cohort among patients with left-sided neuroendocrine carcinomas (HR, 0.55; 95% CI, 0.44-0.68), but not in those with right-sided disease (HR, 0.89; 95% CI, 0.74-1.07).

CONCLUSIONS

Patients with nonmetastatic CRNECs may derive survival benefit from AC. These findings support current guidelines recommending AC in patients with poorly differentiated neuroendocrine carcinomas in the colon and rectum. Efforts in education and adherence to national guidelines for NECs are needed.

Updates on the Role of Molecular Alterations and NOTCH Signalling in the Development of Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) comprise a heterogeneous group of rare malignancies, mainly originating from hormone-secreting cells, which are widespread in human tissues. The identification of mutations in ATRX/DAXX genes in sporadic NENs, as well as the high burden of mutations scattered throughout the multiple endocrine neoplasia type 1 (MEN-1) gene in both sporadic and inherited syndromes, provided new insights into the molecular biology of tumour development. Other molecular mechanisms, such as the NOTCH signalling pathway, have shown to play an important role in the pathogenesis of NENs. NOTCH receptors are expressed on neuroendocrine cells and generally act as tumour suppressor proteins, but in some contexts can function as oncogenes. The biological heterogeneity of NENs suggests that to fully understand the role and the potential therapeutic implications of gene mutations and NOTCH signalling in NENs, a comprehensive analysis of genetic alterations, NOTCH expression patterns and their potential role across all NEN subtypes is required.

The landscape of molecular alterations in pancreatic and small intestinal neuroendocrine tumours

Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs) arise throughout the gut and feature varying biological behaviour and malignant potential. GEP-NENs include two genetically different entities, well-differentiated neuroendocrine tumours (NETs) and poorly differentiated neuroendocrine carcinomas (NEC). NECs are characterized by a dismal prognosis and by distinctive TP53 and RB1 inactivation which sets them apart from NETs. The latter, conversely, have a wide spectrum of aggressiveness and molecular alterations. Knowledge on their biology has recently expanded thanks to high-throughput studies focused on two important groups of well-differentiated neuroendocrine neoplasms: pancreatic (PanNETs) and small intestinal (SiNETs) tumours. PanNETs have been among the most studied also due to genetic syndromes featuring their onset. Research stemming from this observation has uncovered the inactivation of MEN1, VHL, TSC1/2, and the hyperactivation of the PI3K/mTOR pathway as distinctive biological features of these neoplasms. Next-Generation Sequencing added information on the role of telomere lengthening via ATRX/DAXX inactivation in a fraction of PanNETs, while other display shortened telomeres and recurrent chromosomal alterations. The data so far disclosed a heterogeneous combination of driver events, yet converging into four pathways including DNA damage repair, cell cycle regulation, PI3K/mTOR signalling and telomere maintenance. SiNETs showed a lesser relationship with mutational driver events, even in the case of familial cases. High throughput studies identified putative driver mutations in CDKN1 and APC which, however, were reported in a minor fraction (∼10%) of cases. Tumorigenesis of SiNETs seems to depend more on chromosomal alterations (loss of chromosome 8, gains at 4, 5 and 20) and epigenetic events, which converge to hyperactivate the PI3K/mTOR, MAPK and Wnt pathways. While calling for further integrative studies, these data lay previous and recent findings in a more defined frame and provide clinical research with several candidate markers for patient stratification and companion diagnostics.

Genetics and Epigenetics of Gastroenteropancreatic Neuroendocrine Neoplasms

Gastroenteropancreatic (GEP) neuroendocrine neoplasms (NENs) are heterogeneous regarding site of origin, biological behavior, and malignant potential. There has been a rapid increase in data publication during the last 10 years, mainly driven by high-throughput studies on pancreatic and small intestinal neuroendocrine tumors (NETs). This review summarizes the present knowledge on genetic and epigenetic alterations. We integrated the available information from each compartment to give a pathway-based overview. This provided a summary of the critical alterations sustaining neoplastic cells. It also highlighted similarities and differences across anatomical locations and points that need further investigation. GEP-NENs include well-differentiated NETs and poorly differentiated neuroendocrine carcinomas (NECs). NENs are graded as G1, G2, or G3 based on mitotic count and/or Ki-67 labeling index, NECs are G3 by definition. The distinction between NETs and NECs is also linked to their genetic background, as TP53 and RB1 inactivation in NECs set them apart from NETs. A large number of genetic and epigenetic alterations have been reported. Recurrent changes have been traced back to a reduced number of core pathways, including DNA damage repair, cell cycle regulation, and phosphatidylinositol 3-kinase/mammalian target of rapamycin signaling. In pancreatic tumors, chromatin remodeling/histone methylation and telomere alteration are also affected. However, also owing to the paucity of disease models, further research is necessary to fully integrate and functionalize data on deregulated pathways to recapitulate the large heterogeneity of behaviors displayed by these tumors. This is expected to impact diagnostics, prognostic stratification, and planning of personalized therapy.

Gastric hepatoid adenocarcinomas are a genetically heterogenous group; most tumors show chromosomal instability, but MSI tumors do exist

The Cancer Genome Atlas Research Network classified gastric adenocarcinoma into four molecular subtypes: (1) Epstein-Barr virus-positive (EBV), (2) microsatellite-instable (MSI), (3) chromosomal instable (CIN), and (4) genomically stable (GS). The molecular subtypes of gastric hepatoid adenocarcinomas are still largely unknown. We analyzed 52 hepatoid adenocarcinomas for the expression of surrogate markers of molecular subtypes (MLH1, p53, and EBER in situ hybridization) and some biomarkers (p21, p16, Rb, cyclin D1, cyclin E, β-catenin, Bcl-2, IMP3, ARID1A and HER2), and mutations of TP53, CTNNB1, KRAS, and BRAF. We analyzed 36 solid-type poorly differentiated adenocarcinomas as a control group. Hepatoid adenocarcinomas were categorized as follows: EBV group (EBER-positive), no cases (0%); MSI group (MLH1 loss), three cases (6%); "CIN or GS" (CIN/GS) group (EBER-negative, MLH1 retained), 49 cases (94%). In the CIN/GS group, most of the tumors (59%) had either p53 overexpression or TP53 mutation and a coexisting tubular intestinal-type adenocarcinoma component (90%), suggesting that most hepatoid adenocarcinomas should be categorized as a true CIN group. Hepatoid adenocarcinomas showed relatively frequent expressions of HER2 (score 3+/2+: 21%/19%). Hepatoid adenocarcinomas showed shorter survival, more frequent overexpressions of p16 (67%) and IMP3 (98%) than the control group. None of hepatoid adenocarcinomas had KRAS or CTNNB1 mutations except for one case each, and no hepatoid adenocarcinomas had BRAF mutation. In conclusion, gastric hepatoid adenocarcinomas are a genetically heterogenous group. Most hepatoid adenocarcinomas are "CIN," but a small number of hepatoid adenocarcinomas with MSI do exist. Hepatoid adenocarcinomas are characterized by overexpressions of p16 and IMP3.

Identification of high-risk human papillomavirus and Rb/E2F pathway genomic alterations in mutually exclusive subsets of colorectal neuroendocrine carcinoma

Colorectal neuroendocrine carcinomas, both small cell and large cell types, are highly aggressive tumors with poor prognosis compared with colorectal adenocarcinoma. The molecular drivers of neuroendocrine carcinoma are best defined in small cell lung cancer, which shows near-universal genomic alterations in TP53 and RB1. The genetics of colorectal neuroendocrine carcinoma remain poorly understood; recent studies demonstrated infrequent RB1 alterations and genetics closely resembling colorectal adenocarcinoma. To better define the molecular pathogenesis of colorectal neuroendocrine carcinoma, we performed capture-based next-generation sequencing on 25 cases and evaluated for expression of p53, Rb, p16, and high-risk human papillomavirus (HR-HPV) subtypes using immunohistochemistry, in situ hybridization, and polymerase chain reaction. Rb/E2F pathway dysregulation was identified in nearly all cases (23/25, 92%) and occurred via three distinct mechanisms. First, RB1 genomic alteration was present in 56% (14/25) of cases and was accompanied by Rb protein loss, high p16 expression, and absence of HR-HPV; these cases also had frequent genomic alterations in TP53, the PI3K/Ras and Wnt pathways, as well as in DNA repair genes, with 4/14 cases being hypermutated. Second, 16% (4/25) of cases, all left-sided, had TP53 alteration without RB1 alteration; half of these harbored high-level amplifications in CCNE1 and MYC or MYCN and arose in patients with ulcerative colitis. Finally, 28% (7/25) of cases, all rectal or anal, lacked genomic alterations in RB1 or TP53 but were positive for HR-HPV. Our data demonstrate that Rb/E2F pathway dysregulation is essential in the pathogenesis of colorectal neuroendocrine carcinoma, akin to neuroendocrine carcinomas in other anatomic sites. Moreover, colorectal neuroendocrine carcinomas stratify into three distinct molecular subgroups, which can be differentiated based on Rb protein and HR-HPV status. HR-HPV infection represents a distinct mechanism for Rb and p53 inactivation in cases lacking genomic alterations in either gene. Differential treatment strategies for hypermutated and HPV-driven cases could improve patient outcomes.

Colorectal Neuroendocrine Neoplasms: Areas of Unmet Need

The subject of colorectal neuroendocrine neoplasms (NENs), subdivided into well-differentiated NENs, termed neuroendocrine tumours (NETs; grade (G) 1 and 2), and poorly differentiated NENs, termed neuroendocrine carcinomas (NECs; G3) according to the 2010 World Health Organisation (WHO) classification, has arguably not had as much attention or study as NENs occurring in other sites. Colorectal NETs and NECs are however easier to study than many others since they are usually not difficult to remove and are increasingly detected because of intensified colorectal cancer screening and surveillance programmes. Colorectal NETs and NECs show site-specific heterogeneity with variable behaviour and different therapeutic options; these various aspects provide unique challenges. Because of bowel cancer screening programmes, colorectal NENs, like conventional adenocarcinomas, may be diagnosed at a stage that is associated with improved survival. In this article we intend to describe and define areas of unmet needs relating to the epidemiology, classification, pathology, diagnosis and therapy of colorectal NETs (including NETs G3), colorectal NECs, and finally, mixed adeno-neuroendocrine carcinomas (MANECs) by reviewing and discussing the relevant literature.

Advances in the cytologic diagnosis of gastroenteropancreatic neuroendocrine neoplasms

Two-thirds of neuroendocrine neoplasms arising in the human body originate from the gastrointestinal system or pancreas. Gastroenteropancreatic neuroendocrine neoplasms are heterogeneous, comprising both well differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The clinical presentation, molecular characteristics, and behavior are distinct for NETs and NECs. Fine-needle aspiration is an important modality for the primary diagnosis and staging of these neoplasms and can provide information of prognostic and therapeutic significance. Our evolving understanding of neuroendocrine neoplasm biology has led to several iterations of classification. In this review, new concepts and issues most relevant to cytology diagnosis of gastroenteropancreatic neuroendocrine neoplasms are discussed, such as newer detection methods that aid in diagnosis and staging, recent changes in World Health Organization classification, practical issues related to grading these neoplasms on cytology, guidelines for diagnostic reporting, and panels of immunohistochemical stains for the diagnosis of metastasis. The current understanding of genetic and epigenetic events related to tumor development and potential applications for cytology also are presented as they relate to prognostication and recent therapeutic advances.

Establishment of a novel cell line from a rare human duodenal poorly differentiated neuroendocrine carcinoma

Poorly differentiated neuroendocrine carcinoma of the duodenum (D-NEC) is a rare cancer with poor prognosis. However, a D-NEC cell line has not yet been established to study the disease. We established a cell line, TCC-NECT-2, from the ascites tumor of a 59-year-old male Japanese patient with D-NEC. TCC-NECT-2 was positive for neuroendocrine markers, chromogranin A (CGA), cluster of differentiation 56 (CD56/NCAM), synaptophysin (SYN/p38), and neuron specific enolase (NSE). Cells exhibited retinoblastoma (RB) protein loss. Orthotopic implantation of TCC-NECT-2 cells into nu/nu mice resulted in tumor formation (incidence = 83.3%) with neuroendocrine characteristics, metastasis, and weight loss. BRAF^V600E and TP53 mutations and C-MYC gene amplification were also observed in TCC-NECT-2. BRAF^V600E-expressing TCC-NECT-2 cells were sensitive to BRAF inhibitor vemurafenib, and especially dabrafenib, in vitro, and were strongly inhibited in a dose-dependent manner. Dabrafenib treatment (30 mg/kg) in a xenograft model for 14 days significantly suppressed tumor growth (percent tumor growth inhibition, TGI% = 48.04). An enhanced therapeutic effect (TGI% = 95.81) was observed on combined treatment of dabrafenib and irinotecan (40 mg/kg). Therefore, TCC-NECT-2, the first reported cell line derived from D-NEC, might serve as a useful model to study the basic biology of D-NEC and translational applications for treatment.

The Problem of High-Grade Gastroenteropancreatic Neuroendocrine Neoplasms: Well-Differentiated Neuroendocrine Tumors, Neuroendocrine Carcinomas, and Beyond

High-grade gastroenteropancreatic neuroendocrine neoplasms are well-differentiated neuroendocrine tumors or poorly differentiated small/large cell neuroendocrine carcinoma. Distinguishing these entities relies on different genetic backgrounds and resulting different biology. The new classification creates several problems. Almost all clinical treatment data on neuroendocrine neoplasms do not stratify between well and poorly differentiated, providing insufficient help in treatment selection. Treatment of gastroenteropancreatic neuroendocrine neoplasms should separate between well-differentiated neuroendocrine tumors and neuroendocrine carcinoma, and depends on primary tumor site, stage, proliferation rate, and clinical course. This article addresses how to diagnose and treat gastroenteropancreatic neuroendocrine neoplasms, focusing on well-differentiated neuroendocrine tumors versus neuroendocrine carcinomas.

Leucine-rich repeat-containing G-protein-coupled receptor 5 expression and clinicopathological features of colorectal neuroendocrine neoplasms

LGR5 is expressed in various tumors and has been identified as a putative intestinal stem cell marker. Here we investigated LGR5 expression in colorectal neuroendocrine neoplasms and analyzed the correlation with pathological characteristics. We evaluated the clinicopathological features of 8 neuroendocrine tumor (NET) grade 1 (NET G1), 4 NET Grade 2 (NET G2), and 8 NET Grade 3 (NET G3; also termed neuroendocrine carcinoma, or NEC) cases. We examined LGR5 expression using an RNAscope, a newly developed RNA in situ hybridization technique, with a tissue microarray of the neuroendocrine neoplasm samples. LGR5 staining in individual tumor cells was semi-quantitatively scored using an H-score scale. We also performed a combination of LGR5 RNA in situ hybridization and synaptophysin immunohistochemistry. All cases contained tumor cells with some LGR5-positive dots. For all cases, H-scores showed a positive correlation with nuclear beta-catenin expression. In the NEC group, there was a strong positive correlation between H-score and beta-catenin expression. Our findings suggest that LGR5 may serve as a stem cell marker in NEC, as is the case in colon adenocarcinoma. The positive correlation between H-score and beta-catenin expression suggests that LGR5 expression might be affected by beta-catenin expression in neuroendocrine neoplasms and especially in NEC.