Renal leiomyoma. An aspect of differential diagnosis of renal cell carcinoma with increasing clinical significance

Renal leiomyoma is a rare benign tumor which has its origin in smooth muscl e cells of different structures of the kidney. The clinical incidence of re nal leiomyoma is much lower than the frequency described in large autopsy s tudies. Renal leiomyomas are mainly located in the renal capsula and pelvis or next to those structures. Clinical symptoms are nonspecific (e.g., flank pain or flank tumor) or comp letely absent, making most of the leiomyomas an incidental finding during r outine diagnostics. A differential diagnosis between renal leiomyoma and renal cell carcinoma o n the basis of medical imaging is extremely difficult. Therefore, laparotom y and nephrectomy are performed in most cases of suspected renal cell carci noma. The definitive diagnosis of a leiomyoma is only possible after histol ogical examination of the tumor. Due to the rising number of diagnoses resu lting from improved medical imaging, renal leiomyomas are gaining more impo rtance in the differential diagnosis of renal cell carcinoma, especially wi th respect to kidney-sparing surgery.