Sarcomatoid carcinoma of the small intestine: a rare and highly aggressive tumor.

Sarcomatoid carcinoma of the small intestine is an extremely rare malignant neoplasm that usually has a poor prognosis. We report a case of sarcomatoid carcinoma arising in the small intestine in a 62-year-old man who was hospitalized for abdominal pain. Computed tomography revealed wall thickening of the small intestine. The resected specimen showed a gray-whitish solid mass with hemorrhage and necrosis. Microscopically, the tumor was composed of pleomorphic spindle and discohesive polygonal cells with frequent mitosis. No carcinomatous component was recognized. Immunohistochemistry revealed coexpression of cytokeratin and vimentin by the tumor cells, whereas expressions of C-kit, CD34, HMB-45, smooth muscle actin, and desmin were negative. The diagnosis was sarcomatoid carcinoma of the small intestine.