Mucinous anal gland carcinoma with perianal Pagetoid spread.

We report a case of well differentiated perianal mucinous carcinoma with associated dysplasia of the adjacent anal gland epithelium. Anal gland dysplasia is only rarely demonstrable histologically in cases of adenocarcinoma of suspected anal gland origin. The tumor was not associated with chronic perianal abscess or fistula formation, which had been regarded as important in the pathogenesis of perianal mucinous carcinoma. There was associated, clinically unsuspected Pegetoid intra-epidermal spread of adenocarcinoma in the perianal skin.