MELANOMA OF THE ANAL CANAL WITH MELANOSIS OF THE PERITONEUM-CASE REPORT

Abstract

Primary malignant melanoma of the anorectum is rare. It accounts for 0.2-0.3% of all malignant melanomas. Prognosis is very poor since majority of patients dies within first two years. We report a case of a 76 year-old man with anoretal melanoma. Digital rectal examination revealed a mass on the anterior wall. Biopsy report favored two possibilities, first, malignant melanoma and second, poorly differentiated carcinoma. Abdominal ultrasonography and chest X-ray did not show signs of distant metastasis. Computed tomography of abdomen and pelvis revealed presence of a large, irregular hypodense mass with heterogeneous enhancement in anal canal accompanied by enlarged lymph nodes. Abdomino-perineal resection was performed. Histopathological examination of resected specimen confirmed diagnosis of malignant melanoma. Postoperative course was uneventful. However, patient died one year after due to metastasis. Surgery is the mainstay of curative treatment of anorectal melanoma, effective systemic adjuvant therapy has been lacking. Long-term survival is rare, as most patients die of disseminated systemic disease.

Keywords

• malignant melanoma
• anorectum
• abdominoperineal resection.