Tripartite differentiation in a carcinoma of the duodenum

Background. Carcinomas containing three distinctly different cell lines have been encountered in the colon and rectum, but a tripartite malignancy in the small intestine has not been reported previously. Methods. A duodenal carcinoma was studied by light and electron microscopic examination and immunohistochemistry. Results. The duodenal carcinoma was found to have tripartite glandular, squamous, and neuroendocrine differentiation. Histologically, an adenocarcinoma, which originated in a villous adenoma, was continuous with squamous cell carcinoma and small cell carcinoma components. Tumor cells of the squamous cell carcinoma component had conspicuous intercellular bridges but did not form keratin pearls. Immunohistochemical analysis showed strong expression of carcinoembryonic antigen (CEA) by the adenocarcinomatous component. The squamous cell carcinoma component demonstrated focal weak CEA and neuron specific enolase (NSE) reactivity. Ultrastructurally, tumor cells of this component had frequent desmosomes and free tonofilaments. The small cell carcinoma had clusters of dense core granules in tumor cell cytoplasmic processes, which are indicative of neuroendocrine differentiation. This neuroendocrine component was immunoreactive for somatostatin and NSE. Conclusions. This case of tripartite duodenal carcinoma supports the theory of an origin from an intestinal pluripotential stem cell capable of differentiating into multiple cell types.