Gastric neuroendocrine carcinoma associated with chronic atrophic gastritis type A

We report a case of gastric neuroendocrine (NE) carcinoma associated with chronic atrophic gastritis type A (CAG/A) or reversed atrophic type gastritis. A 9 x 6 cm tumor was resected from the stomach to control pain in a 55-year-old Japanese woman with peritoneal dissemination and metastatic tumors of the liver and ovary. Histologically, the tumor was NE carcinoma which showed an organoid structure, but consisted of NE cells with overt cytological atypia and frequent mitotic activity. Multiple microcarcinoids and NE cell micronests (NECMs) were also observed in the atrophic non-neoplastic mucosa of the gastric body. CEA immunoreactivity and a high Ki-67 labeling index were characteristic features of the neoplastic NE cells of the carcinoma. Although most NE tumors arising from CAG/A are typical carcinoid tumors, the present case illustrates that a high-grade NE carcinoma can develop from diverse NE cell proliferation in association with CAG/A.