Epidermoid cyst in the kidney.

We report an extremely rare case of an epidermoid cyst in the kidney of a 74-year-old man who had presented with painless hematuria. Radiologic examination revealed a cyst in the kidney that was thought to be neoplastic. The patient underwent surgery to remove the cyst, and we received the nephrectomy specimen. A 6-cm cyst with no solid areas was seen. On histologic examination, this was an epidermoid cyst. We reviewed the published data and discuss the possible theories of origin of this rare condition......