Composite carcinoid and small cell carcinoma of the duodenum.

A 75-year-old man was admitted to our hospital because of abdominal fullness. Imaging modalities revealed multiple tumors in the liver, but did not detect other tumors. Endoscopic examination revealed an ulcerated tumor in the duodenum. Biopsies were obtained from the duodenal tumor and liver tumors. The duodenal biopsies revealed malignant cells of composite carcinoid and small cell carcinoma. The carcinoid component showed trabecular and ribbon features, and mitotic figures were seen in one per high power fields, thus fulfilling the criteria of typical carcinoid. By contrast, the small cell carcinoma component showed typical small cell carcinoma features. The liver biopsies showed typical small cell carcinoma. The tumors of both organs were argyrophilic. Immunohistochemically, the tumor cells of both organs were negative for gastrin, somatostatin, serotonin, glucagon, and PP, being compatible with a non-functioning tumor. The duodenal and liver tumors were positive for pancytokeratins, epithelial membrane antigen, chromogranin, synaptophysin, CD56, and neuron-specific enolase. By contrast, they were negative for S100 protein, CD45, CD20, CD3, TTF-1, and calcitonin. Cytokeratin 7 was positive in the carcinoid component but negative in the small cell carcinoma component. Cytokeratin 20 was negative in both components and in liver tumors. The Ki-67 labeling was 8% in the carcinoid element and 34% in the small cell carcinoma element in the duodenal tumor, and 38% in the hepatic tumors. The patient died of carcinomatosis 6 months after admission. These findings demonstrate a composite carcinoid and small cell carcinoma in the duodenum. A review of the literature in English language revealed no cases of composite carcinoid and small cell carcinoma in the duodenum.