Tubular adenoma with squamous metaplasia of the sigmoid colon: a case report.

A case of tubular adenoma with squamous metaplasia of the sigmoid colon in a 44-year-old female is reported. The tumor was a pedunculated polyp with a size of 1.2 X 1.7 X 1.7 cm. Histologically, the tumor showed tubular adenoma with focal squamous metaplasia. Borderline atypia was noted in a part of adenoma without squamous metaplasia and squamous component. It is supposed that squamous epithelial polyp, squamous cell carcinoma, adenosquamous carcinoma, and mucoepidermoid carcinoma may be derived from colonic adenoma with squamous metaplasia. Only six cases of the adenoma with squamous metaplasia of the large intestine have been reported previously in the literature.