A suspected case of composite adenoma-carcinoid tumor of the stomach

A flat elevated whitish lesion of 5 mm in diameter was identified in the greater curvature of the antrum in a 73-year-old woman. The biopsy specimen was diagnosed histologically as tubular adenoma. Two years later, endoscopic re-examination was performed and a biopsy revealed endocrine cell micronests (ECMs) at the base of the tubular adenoma. One of ECMs measured greater than 200μm, suggestive of so-called minute carcinoid. ECMs and some cells in the tubular adenoma were positive for synaptophysin and chromogranin A. The tumor was suspected to be a composite adenoma-carcinoma tumor and was treated by endoscopic mucosal resection. The resected specimen was diagnosed as well-differentiated tubular adenocarcinoma with ECMs at the base of the tubular portion. This case report provides important information on histogenesis and differentiation of gastric neoplasms with endocrine features.