[Primary anorectal malignant melanoma--report of 7 cases and review of literature].

From 1956 to 1985, 7 patients with primary anorectal malignant melanoma were studied by clinicopathology and observed by light and electron microscopes. The sex ratio of male and female was 2:5. The mean age was 59.4 years. The main presenting symptoms were bloody stool and a palpable mass in the anus. Because these symptoms are non-specific, early diagnosis is very difficult. The disease course ranged from 1.5 to 21.5 months with an average of 6.7 months. At present, the combination treatment is advocated, and radical operation is still the treatment of choice. This tumor has a very poor prognosis. Grossly, the tumor often showed nodular or polypoid shape. Histologically, there were various forms, such as epithelial, spindle and balloon-like cells etc.. Ultrastructurally, melanin corpuscles and vimentin (intermediate filaments) were found in all. In this paper, pathogenesis, morphology and prognosis are discussed.