Malignant Melanoma of Anal Canal – A Diagnostic Dilemma

ABSTRACT

A 50-year-old male presented with major complaints of bleeding per -rectum and generalized weakness for past one and a half month. Digital rectal examination (DRE) and colonoscopy revealed a thrombosed internal haemorrhoid, which was surgically excised. Histopathological examination (HPE) was pointing towards anal malignant melanoma, which was further confirmed by positive immunohistochemistry (IHC) for HMB-45. As the patient had no secondaries or lymph node enlargement, he was referred for loco-regional radiotherapy. Primary ano-rectal melanoma is a rare but locally aggressive neoplasm capable of early metastasis. Owing to its non-specific clinical presentation it may be mistaken for benign conditions like haemorrhoids and may prove fatal.  Surgical treatment may range from wide local excision (WLE) to abdomino-perineal resection (APR) with controversial role of chemo-radiation in advanced cases. Prognosis is usually bleak with a 5-year survival rate of less than 20%. Owing to the rarity of ano-rectal melanoma and importance of its early detection and management, this case is being reported here.