Anorectal melanoma: clinical characteristics and results of surgical management in twenty-four patients.

Twenty-four patients with primary anorectal melanoma diagnosed since 1974 have been studied retrospectively. There was a predominance of women (2.4:1): Mean age was 64 years. The most common initial symptom was rectal bleeding, typically misdiagnosed as hemorrhoids. Seventeen patients had stage I cancer when first seen, four had stage II, and three had distant disease. Progressive disease most commonly started as a large pelvic mass, diffuse bilateral pulmonary nodules, or diffuse liver metastases. Twenty patients (83%) died of the disease; none survived more than 6 years. Among the patients who died of the disease, median survival was 1.9 years. Median survival for patients with stage I disease (29 months) was longer than that for patients with stage II disease (11 months; p less than 0.05) or stage III disease (9 months). Twelve patients were treated initially with abdominoperineal resection (APR), and three additional patients underwent APR to manage recurrent local or regional disease that developed later in the clinical course. Among evaluable patients with stage I disease initially managed with APR, 50% developed recurrent local-regional disease (mean disease-free interval, 23 months), compared with 100% of those who underwent 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 on both earlier diagnosis and development of more successful therapeutic approaches.