A Case of Synchronous Triple Gastric Cancer with MiNEN (MANEC)

Abstract

A 78-year-old man presented with dyspnea on exertion. An upper gastrointestinal endoscopy showed irregular shaped lesions in the upper, middle, and lower gastric body. A lower gastrointestinal endoscopy showed an ulcerative tumor in the rectum. We diagnosed the case as simultaneous multiple gastric carcinoma (cT2N0M0, cStage I) and rectal carcinoma (cT2N0M0, cStage I), and performed total gastrectomy and anterior resection of the rectum. Macroscopic image of the gastric specimen showed three lesions : (a) type 2 tumor 35 mm in longer diameter in the upper stomach, (b) type 1 tumor 30 mm in longer diameter in the middle stomach, and (c) type 0-IIc tumor 5 mm in longer diameter in the lower stomach. Histopathological examination revealed that the three lesions were (a) mixed adenoneuroendocrine carcinoma (MANEC) (poorly-differentiated adenocarcinoma and neuroendocrine carcinoma), pT2, (b) well-differentiated tubular adenocarcinoma, pT1a, and (c) moderately-differentiated adenocarcinoma, pT1a, respectively. This case was diagnosed as simultaneous triple gastric cancers including a MiNEN (MANEC). Although MANEC is a rare malignant tumor, there are various potential histogenesis. In this case, MANEC appeared as one of multiple gastric adenocarcinomas and NEC existed as it was surrounded by adenocarcinoma tissue. Adenocarcinoma might transform into endocrine component. The coexistence of a rectal cancer suggests abnormalities in mismatch repair genes.