Anal lymphoma presenting as a perianal abscess.

A case of perianal abscess secondary to anal lymphoma affecting a human immunodeficiency virus negative patient is presented. Causes of perianal abscess other than anal glandular infection are important, although the proportion of abscesses reported to be secondary to these other causes is found to vary widely in the literature. A biopsy of the wall of an anorectal abscess should be taken when suspicion of an unusual cause arises.