[Carcinoma of the appendix--rare but important].

Villous adenoma of the vermiform appendix is very rare; the treatment of choice is appendectomy. We report a 72-year-old woman with a villous adenoma and a single focus of invasive, colonic adenocarcinoma. This finding required changes in diagnostic procedures and treatment, and altered the prognosis. The purpose of this report is to increase awareness of this phenomenon and to indicate correct management.