[A case of renal leiomyoma with extensive cystic degeneration]

An extremely rare case of renal leiomyoma presenting as a cystic mass, involving the upper pole of the right kidney in a 59-year-old woman, complaining of right flank pain is reported. Some discussion regarding pathogenesis of leiomyoma with cystic change, diagnostic feature, malignant potential of leiomyoma and others was done. Since 1948, 19 cases including our own case of renal leiomyoma have been reported in the Japanese literature.