Adenosquamous and squamous cell carcinoma of the colon.

Adenosquamous and squamous cell carcinomas of the colon are uncommon tumors; only 28 have been previously reported. In a review of 5,969 colonic adenocarcinomas (excluding anorectal cancers). I identified six carcinomas with squamous features. This is a frequency of 0.1% relative to the incidence of "usual" adenocarcinomas of the colon. An association of squamous neoplasia in the colon and chronic ulcerative colitis is noted.