Retrospective Analyses of PD-L1, LAG-3, TIM-3, OX40L Expressions and MSI Status in Gastroenteropancreatic Neuroendocrine Neoplasms.

We investigated expressions of PD-L1, LAG-3, TIM-3, and OX40L as immune checkpoint proteins, and MSI (repetitive short-DNA-sequences due to defective DNA-repair system) status were analyzed with immunohistochemistry from tissue blocks. Of 83 patients, PD-L1 expression was observed in 18.1% (n = 15) of the patients. None of the patients exhibited LAG-3 expression. TIM-3 expression was 4.9% (n = 4), OX40L was 22.9% (n = 19), and 8.4% (n = 7) of the patients had MSI tumor. A low-to-intermediate positive correlation was observed between PD-L1 and TIM-3 expressions (rho: 0.333, p < 0.01). Although PD-L1 expression was higher in grade 3 NET/NEC, MSI status was prominent in grade 1/2 NET.

Data-independent acquisition combined with liquid chromatography mass spectrometry technique to detect prognostic protein markers in type I gastric neuroendocrine neoplasm.

RATIONALE: This study used proteomics-based data-independent acquisition (DIA) technology with the aim of screening for differential expression proteins in type I gastric neuroendocrine neoplasm (g-NEN). METHODS: Differential expression proteins in type I g-NEN and peritumoral tissues were screened using DIA with liquid chromatography/tandem mass spectrometry (DIA-LC/MS/MS). The identified proteins were then functionally analysed using bioinformatics methods. We selected the three most highly expressed proteins, combined with patients' clinical data, for prognostic analysis. RESULTS: Compared with peritumoral tissues, 224 proteins were up-regulated, and 70 were down-regulated. The most significantly enriched biological processes and pathways were vacuolar proton-transporting V-type ATPase complex assembly and metabolism-related pathways. PCSK1, FBXO2, ACSL1, IRS2, and PTPRZ1 expression was markedly up-regulated in type I g-NENs. High IRS2 expression significantly correlated with a shorter time to recurrence. CONCLUSIONS: Our study provides a comprehensive proteomic signature based on DIA-LC/MS/MS and highlights high IRS2 expression as a potential prognostic marker for type I gNENs.

Pembrolizumab for the treatment of programmed death-ligand 1-positive advanced carcinoid or pancreatic neuroendocrine tumors: Results from the KEYNOTE-028 study.

BACKGROUND: Despite a protracted disease course and multiple available therapies, patients with well-differentiated neuroendocrine tumors (NETs) inevitably experience disease progression. Programmed death-ligand 1 (PD-L1) has been associated with NET progression and prognosis. The multicohort, phase 1 KEYNOTE-028 study (ClinicalTrials.gov identifier NCT02054806) evaluated the activity and safety of the anti-programmed cell death protein 1 immunotherapy pembrolizumab in patients with well-differentiated or moderately-differentiated NETs. METHODS: Patients with PD-L1-positive, locally advanced or metastatic carcinoid or well-differentiated or moderately-differentiated pancreatic NETs (pNETs) were enrolled into separate cohorts and received pembrolizumab at a dose of 10 mg/kg every 2 weeks for up to 2 years. The objective response rate was the primary endpoint (as per Response Evaluation Criteria in Solid Tumors version 1.1, by investigator review). Safety was a secondary endpoint. RESULTS: Of 170 and 106 patients, respectively, who had evaluable samples among those screened for the carcinoid and pNET cohorts, 21% and 25%, respectively, had PD-L1-positive tumors; of these, 25 and 16 patients, respectively, were eligible and treated. The median follow-up was 20 months (range, 2-35 months) and 21 months (range, 5-32 months), respectively. The objective response rate was 12.0% (95% CI, 2.5%-31.2%) and 6.3% (95% CI, 0.2%-30.2%), respectively; 3 partial responses occurred among the carcinoid cohort and 1 among the pNET cohort. The median duration of response in the carcinoid cohort was 9.2 months (range, 6.9-11.1 months), and was not reached in the pNET cohort. No complete responses occurred. Treatment-related adverse events occurred in 68% and 69% of patients, respectively, most often diarrhea (7 patients in the carcinoid cohort and 4 patients in the pNET cohort) and fatigue (6 patients in each cohort). Hypothyroidism was the most common immune-mediated adverse event (5 patients in the carcinoid cohort and 2 patients in the pNET cohort). CONCLUSIONS: Pembrolizumab demonstrated antitumor activity in a subset of patients with NETs and was well-tolerated.

Neuroendocrine Differentiation of Skin Tumors: A Comprehensive Review.

Neuroendocrine differentiation is characterized by endocrine and neuronal features with prominent dense secretory granules and neuropeptides. Neuroendocrine differentiation of skin tumors is of unknown clinical significance. Nonetheless, the acknowledgment of this line of differentiation is important to prevent diagnostic pitfalls and subsequent inappropriate management. This review aims at summarizing the skin neoplasms that can express neuroendocrine markers.

Stage IV lung carcinoids: spectrum and evolution of proliferation rate, focusing on variants with elevated proliferation indices.

The spectrum and evolution of proliferation rates in stage IV lung carcinoids is poorly defined. In particular, there are limited data on the prevalence and characteristics of tumors exceeding the standard upper proliferative criteria-as defined largely based on early-stage carcinoids-in metastatic setting. Sixty-six patients with stage IV lung carcinoids were identified, and all evaluable samples (n = 132; mean 2 samples per patient) were analyzed for mitotic counts and Ki-67 rate. Clinicopathologic and genomic features associated with elevated proliferation rates (>10 mitoses per 2 mm2 and/or >20% hot-spot Ki-67), and evolution of proliferation rates in serial specimens were analyzed. We found that mitoses and/or Ki-67 exceeded the standard criteria in 35 of 132 (27%) samples, primarily (31/35 cases) at  metastatic sites. Although neuroendocrine neoplasms with >10 mitoses per 2 mm2 are currently regarded as de facto neuroendocrine carcinomas, the notion that these cases are part of the spectrum of carcinoids was supported by (1) well-differentiated morphology, (2) conventional proliferation rates in other samples from same patient, (3) genetic characteristics, including the lack of RB1/TP53 alterations in all tested samples (n = 19), and (4) median overall survival of 2.7 years, compared to <1 year survival of stage IV neuroendocrine carcinomas in the historic cohorts. In patients with matched primary/metastatic specimens (48 pairs), escalation of mitoses or Ki-67 by ≥10 points was observed in 35% of metastatic samples; clonal relationship in one pair with marked proliferative progression was confirmed by next-generation sequencing. Notably, escalation of proliferation rate was documented in a subset of metastases arising from resected typical carcinoids, emphasizing that the diagnosis of typical carcinoid in primary tumor does not assure low proliferation rate at metastatic sites. In conclusion, stage IV lung carcinoids frequently exceed the standard proliferative criteria established for primary tumors, and commonly exhibit proliferative escalation at metastatic sites. Despite the overlap of proliferation rates, these tumors show fundamental morphologic, genomic and clinical differences from neuroendocrine carcinomas, and should be classified separately from those tumors. Awareness of the increased proliferative spectrum in metastatic carcinoids is critical for their accurate diagnosis. Further studies are warranted to explore the impact of proliferation indices on prognosis and therapeutic responses of patients with metastatic carcinoids.

Klatskin-mimicking neuroendocrine tumor.

With regard to the article published in your journal by Konstantinos Tsalis et al on Klatskin-mimicking lesions, we recently diagnosed a neuroendocrine tumor (NET) in the proximal biliary tract of a 78-year-old female with obstructive jaundice manifestations. A chest-abdomen-pelvis CT scan identified infiltrating ductal cholangiocarcinoma (Klatskin tumor, type IV in the Bismuth-Corlette classification with cT2N1 staging) and a liver mass in segment IV.

Decrease of 5-hydroxymethylcytosine and TET1 with nuclear exclusion of TET2 in small intestinal neuroendocrine tumors.

BACKGROUND: Small intestinal neuroendocrine tumors (SI-NETs) originate from enterochromaffin cells scattered in the intestinal mucosa of the ileum and jejunum. Loss of one copy of chromosome 18 is the most frequent observed aberration in primary tumors and metastases. The aim of this study was to investigate possible involvement of 5-hydroxymethylcytosine (5hmC), TET1 and TET2 in SI-NETs. METHODS: The analysis was conducted using 40 primary tumors and corresponding 47 metastases. The level of 5hmC, TET1 and TET2 was analyzed by DNA immune-dot blot assay and immunohistochemistry. Other methods included a colony forming assay, western blotting analysis, and quantitative bisulfite pyrosequencing analysis. The effect of the exportin-1 nuclear transport machinery inhibitors on cell proliferation and apoptosis was also explored using two SI-NET cell lines. RESULTS: Variable levels of 5hmC and a mosaic staining appearance with a mixture of positive and negative cell nuclei, regardless of cell number and staining strength, was observed overall both in primary tumors and metastases. Similarly aberrant staining pattern was observed for TET1 and TET2. In a number of tumors (15/32) mosaic pattern together with areas of negative staining was also observed for TET1. Abolished expression of TET1 in the tumors did not seem to involve hypermethylation of the TET1 promoter region. Overexpression of TET1 in a colony forming assay supported a function as cell growth regulator. In contrast to 5hmC and TET1, TET2 was also observed in the cytoplasm of all the analyzed SI-NETs regardless of nuclear localization. Treatment of CNDT2.5 and KRJ-I cells with the exportin-1 (XPO1/CRM1) inhibitor, leptomycin B, induced reduction in the cytoplasm and nuclear retention of TET2. Aberrant partitioning of TET2 from the nucleus to the cytoplasm seemed therefore to involve the exportin-1 nuclear transport machinery. Reduced cell proliferation and induction of apoptosis were observed after treatment of CNDT2.5 and KRJ-I cells with leptomycin B or KPT-330 (selinexor). CONCLUSIONS: SI-NETs are epigenetically dysregulated at the level of 5-hydroxymethylcytosine/ TET1/TET2. We suggest that KPT-330/selinexor or future developments should be considered and evaluated for single treatment of patients with SI-NET disease and also in combinations with somatostatin analogues, peptide receptor radiotherapy, or everolimus.

Loss of expression and prognosis value of alpha-internexin in gastroenteropancreatic neuroendocrine neoplasm.

BACKGROUND: The neuronal intermediate filament alpha-internexin (α-internexin) is a cytoskeleton protein which is involved in the tumor initiation and progression. In this study, we examined the expression and prognosis value of α-internexin in gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). METHODS: α-internexin was detected with immunohistochemical staining in 286 tumor specimens from patients with GEP-NENs. Methylation status of α-internexin was evaluated by bisulfite genomic sequencing. We assessed the prognostic value of α-internexin and its correlation with relevant clinicalpathological characteristics. RESULTS: The reduced/loss of expression rate of α-internexin in GEP-NEN was 73.4% (210/286), while the positive expression rate was 26.6% (76/286). The difference of α-internexin deficiency was not statistically significant between gastrointestinal NENs (GI-NENs) and pancreatic NENs (pNENs). However, we found significant difference of reduced/loss of α-internexin expression among different sites of GI-NENs (χ2 = 43.470, P < 0.001). The reduced/loss of expression of α-internexin was significantly associated with poorly differentiation (P < 0.001) and advanced tumor stage (P < 0.001). Univariate analyses showed that reduced/loss of expression of α-internexin predicted worse overall survival (OS) in GEP-NEN patients (P < 0.001), especially in subtype of GI-NENs (P < 0.001). However, in multivariable regression analysis, α-internexin expression was not an independent prognostic factor. The hypermethylation of α-internexin gene was significantly correlated with protein deficiency in GI-NENs, but not in pNENs. Hypermethylation of several CpG sites was significantly associated with poorly differentiated and advanced stage (P values range from 0.018 to 0.044). However, the methylation status of α-internexin was not associated with patient OS. CONCLUSIONS: The expression of α-internexin was highly heterougeneous in different sites of GEP-NENs. The reduced/loss of expression of α-internexin was closely related to tumors with aggressiveness and patient's adverse prognosis. The hypermethylation of the regulatory region examined may be an important epigenetic regulation mechanism of α-internexin deficiency in subtype of GI-NENs.

Prognostic factors and survival after surgical resection of pancreatic neuroendocrine tumor with validation of established and modified staging systems.

BACKGROUND: Pancreatic neuroendocrine tumors (PNETs) display wide heterogeneity with highly variable prognosis. This study aimed to identify variables related to survival after surgical resection of PNET. METHODS: A total of 143 patients were identified from a prospectively maintained database. Patient characteristics were analyzed and prognostic factors for overall survival and progression-free survival were evaluated. The WHO, ENETS and AJCC scoring systems were applied to the cohort, and their ability to predict patient outcomes were compared. RESULTS: Multivariate analysis found that female gender, lymph node metastases and increasing WHO 2010 grade to be independently associated with reduced overall survival (P < 0.05). Patients requiring multi-visceral resection or debulking surgery found to be associated with shortest survival. ROC analysis found the ENETS and AJCC scoring systems to be similarly predictive of 5-year overall survival. Modified Ki67 significantly improved its accuracy in predicting 5-year overall survival (AUROC: 0.699 vs 0.605; P < 0.01). CONCLUSIONS: Multi-visceral or debulking surgery is associated with poor outcomes. There seems to be no significant difference between enucleation and anatomical segmental resection. Available scoring systems have reasonable accuracy in stratifying disease severity, with no system identified as being superior. Prognostic stratification with modified grading systems needs further validation before applied in clinical practice.

Clinical significance of nestin and its association with survival in neuroendocrine lung tumours.

Nestin is considered to be a cancer stem cell marker. Nestin expression in neuroendocrine tumours might be useful to predict prognosis and facilitate treatment planning. 88 patients with neuroendocrine lung tumours operated in the Department of Thoracic Surgery from 2007 to 2015 were included into the study. Immunohistochemical staining for nestin was performed. Clinicopathological and survival data were retrospectively analyzed. Nestin expression was detected in 15 (17%) specimens. Multivariate analysis showed that lymph node metastases (p = 0.0001; hazard ratio (HR) = 3.93; confidence interval (CI) 95%: 1.96-7.87), nestin expression (p = 0.034; HR = 2.30; CI 95%: 1.06-4.99) and patient's age (p = 0.024; HR = 1.04; CI 95%: 1.00-1.09) were independent negative prognostic factors. Nestin expression was significantly higher in large cell neuroendocrine carcinoma when compared with carcinoids (p = 0.001). Collected data support the thesis that nestin can be regarded as a biomarker in patients with neuroendocrine lung tumours.

[Accurate grading of pancreatic neuroendocrine tumors with Ki-67 index in fine-needle aspiration specimens: a comparative cytologic and histologic study].

Objective: To study the cytomorphologic features and determine whether pancreatic neuroendocrine tumors (PanNET) sampled by fine-needle aspiration (FNA) can be accurately graded based on the Ki-67 index when compared to surgical samples. Methods: Corresponding intraoperative (19 cases) or endoscopic ultrasound-guided (3 cases) FNA cytology and surgical tissue specimens were obtained from 22 tumors, which were reviewed and stained for Ki-67 proliferation marker. The cytological samples included more than 200 tumor cells. Samples were graded by scoring the Ki-67 positive index in accordance with the 2010 WHO criteria. The grading scores assigned to the FNA cytology samples were compared with the scores assigned to the corresponding histological samples. Concordance was achieved by using 5% (instead of 2%) as a cut-off value for defining G2 tumors. One cytological sample included less than 500 tumor cells was excluded in the concordance calculation. Results: The cytological smears consisted of uniform, monotonous and isolated cells, loose cellular aggregates and rosette-like formations. Some tumor cells clustered around segments of capillaries. The cells demonstrated distinct cytoplasmic and nuclear features. Mitoses and necrosis were rarely seen. When traditional 2% Ki-67 index cut-off value were used to classify G2 tumors, the majority (86.4%, κ=0.812, P<0.01) of FNA cytology samples and corresponding surgical tissue specimens demonstrated concordance. When a 5% cut-off value was adopted, the concordance rate was 95.5% (21/22, κ=1.000, P<0.01). Similar concordance rates between the cytological and histological grades were achieved with threshold value of cytological assessment material set at more than 500 or 200 cells. Conclusions: The cytological Ki-67 index in adequate material (>200 tumor cells) is useful in grading pancreatic neuroendocrine tumors, and a cut-off value of 5% showed better predictive value compared with that of 2%. Accurate grading of PanNET is critical for predicting tumor biology, patient prognosis, and making informed decisions regarding patient management and treatment.

Comparison of metastatic neuroendocrine neoplasms to the breast and primary invasive mammary carcinomas with neuroendocrine differentiation.

Metastatic neuroendocrine neoplasms to the breast may show considerable morphologic overlap with primary mammary carcinomas, particularly those showing evidence of neuroendocrine differentiation, and may be misdiagnosed as such. Accurate distinction between these two entities is crucial for determination of appropriate clinical management. The histologic and immunohistochemical features of metastatic neuroendocrine neoplasms to the breast were studied and compared with the features of primary invasive mammary carcinomas with neuroendocrine differentiation, which served as controls. Of the metastatic neuroendocrine neoplasms, 15 were well-differentiated neuroendocrine tumors with carcinoid tumor-type morphology and 7 were poorly differentiated/high-grade neuroendocrine carcinomas with small-cell or large-cell neuroendocrine carcinoma morphology. The majority of the metastatic neoplasms originated in the lung and gastrointestinal tract. There were histologic similarities between metastatic neuroendocrine neoplasms and invasive mammary carcinomas with neuroendocrine differentiation, both of which exhibited neuroendocrine histologic features (nested and trabecular architecture, minimal tubular differentiation, and characteristic nuclear features). Only one case of the invasive mammary carcinomas with neuroendocrine differentiation was modified Bloom-Richardson grade 1 (largely due to minimal tubular differentiation on most such tumors), and the invasive mammary carcinomas with neuroendocrine differentiation were often associated with in situ carcinoma. Immunohistochemistry was helpful in distinguishing metastatic neuroendocrine neoplasms from invasive mammary carcinomas with neuroendocrine differentiation. Whereas the majority of invasive mammary carcinomas with neuroendocrine differentiation were positive for estrogen receptor and GATA3, metastatic neuroendocrine neoplasms were typically negative for estrogen receptor and GATA3, and metastatic well-differentiated neuroendocrine tumors often showed immunoreactivity for site-specific markers. Although the histologic and immunohistochemical features of a breast tumor may raise the suspicion of a metastatic neuroendocrine neoplasm, the pathologic findings should be interpreted in the context of the clinical history and imaging findings in order to establish an accurate diagnosis.

Pancreatic neuroendocrine tumors in twelve baboons (Papio spp.).

BACKGROUND: Pancreatic neuroendocrine tumors (PNETs) are rare in nonhuman primates and in humans. METHODS: Twenty-one PNETs from twelve female baboons (Papio spp.) from the Southwest National Primate Research Center were evaluated using histopathology and immunohistochemistry. RESULTS: Histologically, all tumors were benign and had neuroendocrine packeting. Immunohistochemical staining for synaptophysin and chromogranin was positive in all tumors evaluated (17/17). Insulin was positive in 16 of 21 tumors. Somatostatin was positive in 9 of 20 tumors. Multifocal staining for glucagon and pancreatic polypeptide was evident in a minority of tumors (6/20 and 2/17, respectively). Gastrin and vasoactive intestinal peptide were negative in all tumors evaluated. Nine tumors expressed more than one hormone marker. CONCLUSIONS: This is the first detailed pathologic study of pancreatic endocrine tumors in the baboon. The findings suggest that these tumors are generally benign and have similar morphologic and immunohistochemical features as those described in people, including the ability to express multiple hormones.

[Pulmonary neuroendocrine tumors and preneoplasic lesions]. / Tumeurs neuroendocrines pulmonaires et lésions prénéoplasiques.

In the recently published 2015 World Health Organization (WHO) classification of tumors of the lungs, all neuroendocrine tumors of the lungs are presented for the first time in one single chapter. In this classification, high-grade small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) are differentiated from intermediate grade atypical carcinoids (AC) and low-grade typical carcinoids as well as from preinvasive lesion diffuse neuroendocrine hyperplasia DIPNECH. In the 2004 WHO classification, SCLC and carcinoids each had a separate chapter and LCNEC was listed in the chapter on large cell carcinoma of the lungs. The new WHO classification also gives some recommendations for the diagnosis on small biopsies. This review describes morphological, immunohistochemical, and genomic characteristic of these tumors according to the new classification.

Gastrointestinal neuroendocrine tumor with unresectable liver metastases: an example of multimodal therapeutic approach.

Gastrointestinal neuroendocrine tumors (NET) frequently present with unresectable hepatic metastases, which poses a barrier for curative treatment. Resection of the primary tumor and subsequent orthotopic liver transplantation (OLT) has been proposed as a treatment approach but available data in this regard is limited. We present a clinical case of an otherwise asymptomatic 44-yo man complaining of abdominal pain and dyspepsia that was diagnosed of a 10 cm duodenal tumor with multiple hepatic metastases. A CT-guided biopsy confirmed a NET. He underwent first a Whipple's procedure, and then was listed for liver transplantation. During the waiting time a multimodal therapeutic approach was used including the use of radioactive 177lutetium-labeled somatostatin analogues, long-acting somastostatin analogues and antiangiogenic antibodies (bevacizumab) in order to keep neoplastic disease under control. Two years after Whipple's procedure and given disease stability he underwent OLT with an uneventful postoperative evolution. Patient condition and graft function are optimal after a 4-year follow-up period with no evidence of recurrence. This case report underscores how a multimodal approach involving careful patient selection, resective surgery as well as use of somatostatin analogues and antiangiogenic biological therapy followed by liver transplantation can achieve excellent long-term results in this difficult patient population.

What clinicians are asking pathologists when dealing with lung neuroendocrine neoplasms?

Lung neuroendocrine tumors (NET) are currently classified in resection specimens according to four histological categories, namely typical carcinoid (TC), atypical carcinoid (AC), large-cell neuroendocrine carcinoma (LCNEC) and small cell carcinoma (SCC). Diagnostic criteria have remained unchanged in the 2015 WHO classification, which has ratified the wide acceptance and popularity of such terminology in the pathologists׳ and clinicians׳ community. A unifying umbrella of NE morphology and differentiation has been recognized in lung NET, which has pushed to enter an unique box of invasive tumors along with diffuse idiopathic pulmonary NE cell hyperplasia (DIPNECH) as a pre-invasive lesion with a potential toward the development of carcinoids. However, uncertainties remain in the terminology of lung NET upon small samples, where Ki-67 antigen could play some role to avoid misdiagnosing carcinoids as high-grade NE tumors. Epidemiologic, clinical and genetic traits support a biological three-tier over a pathology four-tier model, according to which TC are low malignancy tumors, AC intermediate malignancy tumors and LCNEC/SCC high malignancy tumors with no significant differences in survival among them. Inconsistencies in diagnostic reproducibility, troubles in the therapy of AC and LCNEC, and limitations to histology within the same tumor category argue in favor of a global re-thinking of lung NET where a grading system could play a role. This review outlines three main key questions in the field of lung NET: (A) unbiased diagnoses, (B) the role of Ki-67 and tumor grading, and (C) management of predictive markers. Answers are still inconclusive, thus additional research is required to improve our understanding on lung NET.

Problems with the diagnosis of metastatic neuroendocrine neoplasms. Which diagnostic criteria should we use to determine tumor origin and help guide therapy?

Neuroendocrine neoplasms (NENs) can often present with metastatic disease before the primary tumor is discovered. Metastatic lesions are generally classified as well differentiated and poorly differentiated for prognostic and therapeutic purposes. In addition, for well-differentiated neuroendocrine tumors (WDNETs), pathologists are expected to determine the site of origin, if not already known, and grade the tumors. However, it is often difficult for pathologists to provide this information with certainty without knowing the site of tumor origin, as different criteria have been proposed by WHO for classification of gastrointestinal and pulmonary NENs. In this review, we will discuss the current classification and grading schema of NENs and their impact on clinical care, the differential diagnosis of NENs, the use of immunohistochemical stains that help identify tumor site of origin, and a proposed approach for the diagnosis and classification of metastatic NENs.

Neuroendocrine neoplasms of the lung: Concepts and terminology.

Neuroendocrine neoplasms of the lung continue to undergo scrutiny, with respect to the diagnostic terminology recommended for them and details of their clinicopathologic profiles. This overview considers the nosological evolution of such lesions and presents current views on classification schemes that pertain to them.

Clinical characteristics and prognostic factors of gastroenteropancreatic neuroendocrine tumors: a single center experience in China.

BACKGROUND/AIMS: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a unique subgroup of tumors in the digestive system but with great clinical heterogeneity. The information on clinical characteristics and prognostic factors of Chinese patients is rather limited. METHODOLOGY: We retrospectively analyzed the clinical features, prognostic factors of this disease in a consecutive cohort (N=294) between January 2007 and December 2012. RESULTS: Functioning tumors accounted for 9.2%. Rectum was the most predominant GEP-NETs locations. Abdominal pain occurred in 46.5% patients which was the most common initial symptom. G1, G2 and G3 tumors accounted for 41.5%, 34.7% and 23.8%, respectively. Endoscopy provided the highest detection rate of 95.7%. Consistence between endoscopic ultrasound guided fine needle aspiration biopsy (EUS-FNAB) and surgically obtained histological Ki-67 index was 36.4%. Serum CgA test showed a 80.0% consistence with the tissue biopsy. The median follow up duration was 2.8 years (0.02-5.90 years), the median survival was 4.8 years, overall 5-year survival rate was 69.6%. We found colonic localization, tumor size larger than 20 mm, G3 tumor and metastasis were associated with worse outcome (p<0.05). CONCLUSION: We found both consistence and differences in GEP-NETs characteristics between our study and previous reports.