Immunohistochemical consistency between primary tumors and lymph node metastases of gastric neuroendocrine carcinoma

Background: Gastric neuroendocrine carcinoma (G-NEC) is a rare, highly malignant tumor that exhibits aggressive growth leading to vascular invasion, distant metastasis and extremely poor prognosis. We studied the clinicopathological findings of seven patients at our institute to better under this disease. Methods: Seven cases of G-NEC were identified among 1,027 cases of gastric carcinoma that underwent gastrectomy at Kansai Rousai Hospital between 2002 and 2010. We studied the pathological and immunohistochemical features of gastric neuroendocrine carcinomas at both the primary site and metastatic lymph nodes. Results: The mean patient age was 73 years (range 63 to 86 years). There were no females in this series. The final staging was Stage I in one case, Stage II in two, Stage III in two and Stage IV in two. A total of 31 metastatic lymph nodes were found in these patients. This study revealed that the ratio of neuroendocrine cells was similar between the primary and metastatic sites, which tended to show the same expression patterns of neuroendocrine markers. Conclusions: Metastatic lymph nodes showed heterogeneous immunohistochemical expression patterns similar to the primary sites. G-NEC is far advanced at diagnosis and rapidly reaches the lymph nodes retaining its heterogeneity, carrying a worse prognosis than common gastric cancer. Mini abstract: G-NEC grows rapidly and metastasizes to the lymph nodes, retaining its pathological and immunohistochemical heterogeneity even at the metastatic sites.