Gastric neuroendocrine carcinoma: Clinicopathologic review and immunohistochemical study of E-cadherin and Ki-67 as prognostic markers

Background and Objectives: Gastric neuroendocrine carcinoma (NEC) is an uncommon cancer of the stomach. The classification of NEC and its clinical behavior remains controversial, and prognostic markers and their therapeutic guidelines have not been clearly defined. The aim of this study was to evaluate the clinicopathologic characteristics of these tumors and analyze the expression of E-cadherin and Ki-67 as prognostic markers in gastric NECs. Methods: We retrospectively reviewed 17 cases of gastric NECs. Tumor pathology was reviewed and the tumors were categorized as well-differentiated NEC (n = 5) and poorly differentiated NEC (n = 12) according to the WHO classification. With the aim of evaluating the expression of E-cadherin and Ki-67 and their prognostic role in gastric NEC, immunohistochemical analysis of the tumors was performed. Results: The median survival of patients was 20.0 months (95% confidence interval (CI), 13.2-28.8). There was a statistically significant difference in overall survival between well and poorly differentiated NECs (P=0.021). However, there was no significant difference in overall survival between patients with poorly differentiated small cell and large cell NEC (P = 0.796). Loss of E-cadherin was correlated with lymph node metastasis (P = 0.044). A high Ki-67 proliferation index (PI) (>60%) was correlated with tumor recurrence (P=0.013) and histologic differentiation (P= 0.028). Conclusions: Loss of E-cadherin may predict lymph node metastasis in gastric NECs. A high Ki-67 PI (>60%) could be used as a prognostic marker to predict aggressive gastric NECs in addition to standard pathologic classification.