Cystic hamartoma of the renal pelvis.

Cystic hamartoma of the renal pelvis is a rare benign tumor in the same category as mixed epithelial and stromal tumors. We present a 33-year-old woman with a solid and cystic intrarenal tumor extending into the renal pelvis. She underwent radical nephrectomy and ureterectomy under the diagnosis of renal tumor or renal pelvic tumor. Histopathologically, the tumor was composed of a biphasic proliferation of epithelial and mesenchymal elements. We believe the present case is best classified as a cystic hamartoma of the renal pelvis in the category of mixed epithelial and stromal tumors because of the coexistence of hamartomatous lesions, such as the proliferation of adipose cells and well to poorly differentiated fibromuscular lesions.