Choriocarcinoma of the colon.

Primary choriocarcinoma of the colon is exceedingly rare. Only two cases have been previously reported, both located in the sigmoid colon. A case of choriocarcinoma arising in association with adenocarcinoma of the ascending colon (cecum) in a 35-year-old woman is described. Immunoperoxidase staining showed beta-human chorionic gonadotrophin to be present in the choriocarcinomatous portion of the primary tumor and in the metastases. Theories concerning the histogenesis of this rare neoplasma are briefly reviewed.