Renal masses simulating primary renal cell carcinoma in patients with advanced malignancies

Most patients who present with a large solid renal mass and evidence of advanced malignancy will have primary renal cell carcinoma but a small subset with similar features have different and more treatable malignancies. We identified 7 patients with clinical and radiological findings suggestive of metastatic renal cell carcinoma who were ultimately diagnosed as have non-Hodgkin's lymphoma (5), germ cell tumor (1) or transitional cell carcinoma (1). Two of these patients presented with abdominal pain, gross hematuria and a flank mass. Computerized tomography was interpreted as showing renal cell carcinoma in all patients, although lymphoma and sarcoma were included in the differential diagnoses in 2. With the correct diagnosis and appropriate therapy, 4 of the 7 patients are currently disease-free. We emphasize the need for histological documentation in such patients in view of curative therapy available for possible underlying neoplasms simulating renal cell carcinoma.