Renal sinus leiomyoma mimicking papillary renal cell carcinoma: A case report.

Renal leiomyomas are rare benign tumors that predominantly affect women in their 40s and 50s. Here, we report a case of renal leiomyoma originating from the renal sinus of a woman in her 30s. The lesion was incidentally discovered on abdominal magnetic resonance imaging as a 4 cm, well circumscribed mass with smooth margins located in the right renal sinus. Dynamic contrast-enhanced computed tomography (CT) revealed homogenous and progressive enhancement, while T2-weighted magnetic resonance imaging (MRI) demonstrated uniformly low signal. Although imaging findings suggested a renal sinus tumor, papillary renal carcinoma could not be definitively excluded by imaging. Due to the difficulty in performing computed tomography-guided biopsy, a nephrectomy was undertaken. Pathological examination confirmed the diagnosis of a renal leiomyoma originating from the renal sinus.