The first case of renal lipoma in a child.

Lipoma of the kidney is a rare benign renal tumor that previously had been reported only in adults. We present a case of this tumor in a 2-year-old boy. Serial imaging studies revealed a tumor with high fat content arising from the right kidney. Radical nephrectomy was performed for tumor excision. Macroscopically, the tumor consisted of a yellow fatty mass, which was surrounded by a thin fibrous capsule. The tumor was about 600 g, and the kidney was compressed laterally by the tumor. Microscopically, the tumor consisted of large fat cells that did not express human melanoma black-45 (HMB-45). It was diagnosed as a renal lipoma. Postoperatively, there has been no recurrence of tumor in the 10 months since the surgical excision.