Mixed epithelial and stromal tumor of the kidney.

A 42-year-old female presented with intermittent left flank pain for 2 years. She developed gross hematuria 1 month prior to seeking help. Intravenous pyelography showed filling defects within the lower portion of the left collecting system and renal pelvis causing hydronephrosis. Abdominal computed tomography revealed a huge cystic heterogenic tumor about 20 cm in largest diameter occupying the entire left kidney. A left radical nephrectomy was performed without complications. The pathology report confirmed the diagnosis of mixed epithelial and stromal tumor of the kidney. From pathologic survey, the spindle cells of this tumor were positive for muscle markers and expressed estrogen and/or progesterone receptors. We suggest that a mixed epithelial and stromal tumor of the kidney should be considered in all cystic renal tumors presenting in perimenopausal women.