[Benign tumors of the kidney]

Benign tumors of the kidney were rare entities in the incidence. But, recently, the cases with benign tumors of the kidney which were discovered incidentally have increased by popularization of ultrasonography and computed tomography. It is easy to distinguish a mass on clinical examination, but it is difficult to differentiate definitely either benign tumor or malignant one clinically. Besides, it has been pointed out that cases of renal oncocytoma had fairly been included among the nephrectomized cases because of the diagnosis as renal cell carcinoma. Consequently, we need sufficient knowledge about benign tumors of the kidney. Author discussed an outline of the representative benign tumors of the kidney.