[A case report of carcinoid of the rectum coexisting with adenocarcinoma in a single lesion].

A 69-year-old female, chiefly complaining of diarrhea, was admitted to the Toyama Medical & Pharmaceutical University Hospital. A barium enema and an endoscopic examination revealed a villous adenocarcinoma of the rectum. Computerized tomography disclosed multiple metastatic lesions in the liver. She underwent an amptatio recti and an intra-arterial cannulation of the common hepatic artery in order to administer anticancer agents. Gross findings of the resected specimen showed villous adenocarcinoma containing a small ulcerated lesion. Histologic findings of this lesion revealed a collision neoplasm containing both an adenocarcinoma and a carcinoid with no obvious transitional region between the two lesions. The type D carcinoid, determined according to Soga's histologic classification, showed positive argyrophil granules but no argentaffin granules in the cytoplasm. The electron-microscopic findings of the carcinoid revealed small electron-dense endocrine granules measuring about 150 approximately 300 nm in diameter. The woman died 4 months after this operation.