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

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

Automated summary

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