Anal carcinoma presenting as a perirectal abscess or fistula.

In five years, 15 patients were seen with anal carcinomas presenting as perirectal abscesses or fistulas. Nine patients had acute abscesses without histories of chronic anorectal disease, and six patients had long-standing anorectal disease in which carcinoma developed. Operative exploration was needed to establish the diagnosis in all patients. Early definitive surgery would certainly have prevented most if not all of the cancers from developing in the group with chronic anorectal disease.