Anorectal melanoma: clinical characteristics and the role of abdominoperineal resection.

Twenty-four patients with primary anorectal melanoma diagnosed since 1974 have been retrospectively studied. The most common presenting symptom was rectal bleeding, typically misdiagnosed as hemorrhoids. Progressive disease most commonly presented as a large pelvic mass, diffuse bilateral pulmonary nodules, or diffuse liver metastases. Twenty-one patients (88%) died of their disease; none survived more than 6 years. Among the patients who have died of their disease, mean survival was 2.2 years. Among assessable stage I patients initially managed with abdominoperineal resection (APR), 50% developed recurrent local regional disease (mean disease-free interval = 23 months), compared with 100% of those managed with more limited surgery (mean disease-free interval = 16 months). Even after APR, however, distant metastases were common, and there was no prolongation of survival for patients treated with APR. Primary melanoma of the anorectum has a high metastatic potential and carries a grave prognosis. APR appears to have some effect in controlling local and regional disease, but prolongation of survival will depend both on earlier diagnosis and on development of more successful therapeutic approaches.