[Symptomatic leiomyoma of the kidney: renal mass with difficult preoperative diagnosis].

Renal leiomyoma is a benign mesenchymal tumour that, albeit very rare, has to be ruled out when a renal mass has been diagnosed. This tumour can arise from any organ of the genitourinary tract with smooth muscle cells, being the renal capsule the most frequent origin. As its behaviour is not aggressive, nephron-sparing surgery is indicated. However, as it is difficult to preoperatively differentiate the leiomyoma from the adenocarcinoma, the former is commonly diagnosed after examination of the entire organ surgically removed.