RESUMO
Anorectal melanoma is one of the rare but significant malignancies of the anorectal area. This malignancy currently accounts for 1% of all types of melanoma and less than 1% of all the anorectal area malignancies. Very rare cases of this disease have been reported worldwide. Anorectal melanoma is mostly diagnosed while treating other benign conditions of this area such as hemorrhoids with conventional modalities. Its treatment of choice has always been a controversial issue. In this study, clinical pathology and outcome of 7 cases with anorectal melanoma referred to Omid Oncology Teaching Hospital during 2001-2011 were assessed. Out of seven cases, 2 patients had been diagnosed with hemorrhoids and undergone surgery and 2 other cases had been referred with the primary diagnosis of lymphoma. Initially, only in 3 cases melanoma was diagnosed in clinico-pathology setting. Three cases of patients had distant metastases to the liver, lungs, omentum and mesentery, while the other 4 patients had advanced local disease. No patient had been diagnosed in the primary stages of the disease. The mean time duration between symptoms onset to diagnosis of disease had been 8 months. The median survival time was 5 months. Rare anorectal melanoma and its similar manifestations to other common anorectal conditions can delay the diagnosis, therefore should be considered as an uncommon differential diagnosis. The disease's outcome is poor and most probably delay in the diagnosis has an important role in the treatment results.