[Primary ileal adenocarcinoma, showing squamous differentiation and ossification]

A 55-year-old man underwent an ileocecal resection because of an intestinal obstruction. The resected specimen contained a sessile tumor near the ileal end. This tumor was 9 x 7 cm in size, with a nodular surface of brown tint. Microscopically, it was a well-differentiated adenocarcinoma, the tumor tissue extending into the muscularis propria. The malignant tissue was associated partially with adenomatous areas and, in malignant nests, with foci of lamellar and intracellular cornification. Further, there was focal ossification in the fibrous stroma. Stains for argyrophil and argentaffin cells revealed strong positive reactions, and immunohistochemical studies were positive for calcitonin and CEA. These findings suggest the multi-potentiality of a small intestinal carcinoma.