Composite carcinoid-adenocarcinoma tumor of the stomach: report of a case.

We describe herein the case of an extremely unusual composite carcinoid-adenocarcinoma tumor of the stomach, most of which was found to be carcinoid. The carcinoid tumor component exhibited argyrophilic granules, immunohistochemical localization of chromogranin, and serotonin immunoreaction. Conversely, none of the adenocarcinoma component reacted with argyrophilia, chromogranin, or serotonin. DNA flow cytometric analysis revealed a near-diploid pattern in the carcinoid element and an aneuploid pattern in the adenocarcinoma element. The transitional zone and continuity between the two tumor components were observed. These findings suggest that the tumor originated from the endocrine system, although part of it showed nonendocrine differentiation. The patient died approximately 6 months after the onset of symptoms and an autopsy could not be performed.