Adenocarcinoma of a colostomy following abdominoperineal resection for squamous cell carcinoma of the anal canal: a case study.

Malignant neoplasms presenting on a stoma, as well as the development of colorectal adenocarcinoma after previous treatment for squamous cell carcinoma (SCC) of the anal canal, are rare. The unique case is presented of an 81-year-old woman with parastomal bleeding and ulceration found to have a primary colorectal adenocarcinoma arising de novo on a colostomy, formed after salvage abdominoperineal resection (APR) 3 years earlier for recurrent anal SCC. This is the first reported case of a colonic adenocarcinoma on a colostomy formed after an APR for anal SCC. Although stomal neoplasia is rare, the appearance of a friable bleeding lesion on the stoma should be investigated to exclude metastatic cancer or a second primary malignancy.