Adenocarcinoma of unknown primary in a 20-year-old African American male.

A 20-year-old African American male presented with a history of left flank pain and passing of light pink urine. Medical history included sickle cell trait. Urine analysis was positive for protein and blood. Metabolic profile, autoantibody screen, and complement levels were normal. Hemoglobin electrophoresis revealed an 41.8% HbS diagnostic of sickle cell trait. Creatinine clearance was normal and proteinuria was nonnephrotic. A noncontrast computed tomography (CT) scan showed left proximal hydronephrosis. Urology follow-up was arranged and the differential included renal papillary necrosis, or renal cyst rupture. He presented 3 months later with sudden onset left flank pain and gross hematuria. Serum creatinine was 1.8 mg/dL. Computed tomography scan with contrast revealed innumerable lung lesions, an enlarged heterogenously enhancing left kidney, and retroperitoneal adenopathy. Ultrasound revealed an obstructed left collecting system and a 14-cm enlarged left kidney with no discrete mass. Testicular markers/ultrasound, upper/lower endoscopies were normal. Lung biopsy revealed poorly differentiated adenocarcinoma positive for cytokeratin 7. Renal, sarcoma, and gastrointestinal markers were negative. By exclusion, it appeared that the patient had a carcinoma of unknown primary. However, with the clinical and personal history, a diagnosis of renal medullary carcinoma (RMC) was made. RMC is a rare and highly malignant tumor that should always be included in the differential of a patient with sickle cell disorder and hematuria. Renal biopsy typically fails to sample the renal medulla and radiologic findings might not raise the suspicion of a renal tumor. Thus, clinical suspicion must always be high in order to preserve the patient's only chance of prolonged survival.