PRIMARY ANORECTAL MELANOMA - 9 CASES

We report nine cases of anorectal melanoma illustrating the histopatho logical features of these tumors. In all cases, the diagnosis was made at symptomatic stage. Eight patients were treated by surgical procedu re which consisted of abdominal perineal resection or local excision. The tumor was either monomorphous, composed of epithelioid or spindle cells, or polymorphous containing both cell types. One case was charac terized by small cells resembling plasma cells. Pigmentation was incon stant. Tumor cells were marked by antibodies directed against the S100 protein (9 cases/9), HMB45 (4 cases/7) and vimentin (5 cases/7). As s uggested by these cases, the diagnosis of melanoma should be systemati cally kept in mind in case of an anorectal tumor with unusual histopat hological features.