Renal leiomyosarcoma: a diagnostic challenge.

Renal leiomyosarcoma is a very rare tumor that clinically and radiographically mimics more common renal malignancies. The infrequency of the condition makes it very difficult to diagnose. A 70-year-old male smoker presented with months of hematuria, right-sided flank pain, and weight loss. Imaging revealed a 3.8-centimeter renal mass that had characteristics similar to renal cell carcinoma. Initial biopsy of the mass was negative for malignancy. Two months later, subsequent imaging revealed what appeared to be metastatic bone lesions. Again, a biopsy of one of the lesions was negative for malignancy. Subsequent ureteral pyeloscopy, ureteroscopic renal pelvis biopsy, and brush cytology were negative for malignancy as well. The decision was made to perform nephrectomy for the removal of the mass. Pathologic analysis revealed renal leiomyosarcoma. This case illustrates the difficulty in diagnosing renal leiomyosarcoma. Repeated pathologic sampling was negative because of the tumor heterogeneity. Prompt diagnosis and treatment are very significant as surgical resection at an early stage offers the best prognosis.