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Malignant melanoma presenting as a retroperitoneal mass is a rare manifestation of this disease. Melanoma, a malignant tumor of melanocytes, is a form of skin cancer with about 160,000 new cases of melanoma yearly worldwide. More than 53,000 people in the United States are diagnosed with melanoma every year. We present a rare case of malignant melanoma presenting as a retroperitoneal mass. Case reportA 77 year old African American male presented with fatigue, abdominal pain, decreased appetite and 40 lbs weight loss over the period of 2-3 months. The patient had a CT scan of the abdomen and pelvis done as an outpatient which demonstrated a large heterogeneous, lobulated mass in the sub hepatic space measuring approximately 16.7cm × 11cm × 13 cm (Figure 1). This was thought to be a retroperitoneal mass. He was noted to have new onset anemia with positive stool hem occult. The patient was admitted to the hospital for further evaluation. His past medical history was remarkable for hyper lipidemia and benign prostatic hypertrophy. He is a former smoker and denied alcohol or illicit drug use. The patient was noted to be a cachetic, frail elderly man. Cardiopulmonary evaluation was unremarkable. Abdomen was soft with tenderness and fullness in the right upper quadrant, bowel sounds were present. Skin exam did not reveal any lesions. His white blood cell count was 6.5 × 10 3 ; Hemoglobin 9.6 and platelet count 451 K. His basic chemistry panel was within normal limits. The patient received two units of packed red blood cells with appropriate response. He underwent an endoscopic evaluation for the GI bleed. Endoscopy revealed a mass infiltrating the duodenum. This infiltration of the mass was not appreciated on the previous CT scan. The patient underwent a PET/CT. The PET/CT again showed a large heterogeneous, lobulated sub hepatic mass. The peripheral aspect of the mass had intense FDG activity. Central portions of the mass were not FDG-avid, suggesting that they were necrotic. Two small hyper metabolic foci were seen in the liver, consistent with metastases.

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