Synchronous primary adenocarcinoma and ancient schwannoma in the colon: an unusual case report.

Gastrointestinal schwannomas are uncommon stromal tumors of the intestinal tract and colon schwannomas are extremely rare. We report a rare case of ascending colon schwannoma with associated synchronous adenocarcinoma of the sigmoid colon. A 68-year-old man presented with a 20-day history of bleeding per rectum. Colonoscopy revealed a mass of 4.2 cm in diameter with endoluminal protrusion in the sigmoid colon and a second submucosal tumor in the ascending colon. Surgical intervention was suggested and ileo-hemicolectomy was done. Microscopically, the submucosal tumor of 4 cm in diameter showed features of schwannoma with degenerative change (ancient schwannoma). Lesional cells were positive for S100p and negative for actin, desmin, CD34, CD117, and pankeratin. The mass showed features of an invasive moderately differentiated adenocarcinoma. Colon schwannoma is a rare submucosal tumor, and the incidental occurrence with adenocarcinoma has not been well described in the literature.