Bloody Stool as the Presentation of Melanoma of Unknown Primary Origin

This is a report on a 78-year old patient with a history of scleroderma, presenting with fresh bloody stools for one month. Colonoscopy revealed black masses in the ascending colon and rectum and biopsy confirmed the diagnosis of malignant melanoma. Abdominal CT revealed metastasis to the liver and both adrenal glands. Positron emission tomography (PET) was conducted to locate the primary site but no lesions were found on the skin. Thus, the primary site of the malignant melanoma in this case remained unknown. The case report is followed by a literature review.