Giant leiomyoma of the renal capsule: CT and MR imaging features with pathologic correlations

Renal leiomyoma (RL) is a rare benign tumor, usually presenting as a small asymptomatic lesion, frequently found during autopsy with a higher incidence in women (2:1). However, larger RL can become symptomatic and show structural changes (such as hemorrhagic and cystic degeneration), thus posing a diagnostic challenge. A 49-year-old woman with a recent history of weight loss and left flank pain was referred to our institution. An ultrasound exam revealed the presence of a complex mass at the left kidney. Both CT and MRI scans were performed to characterize the renal mass, which appeared well circumscribed with no signs of local invasion. Moreover, CT and MRI provided valuable additional information such as the absence of both macroscopic and microscopic fat and the presence of calcifications, hemorrhagic areas, multiple cysts and delayed enhancement. A left nephrectomy was performed via laparoscopy. Histopathological evaluation confirmed the diagnosis of RL. Imaging techniques can aid in the identification of large RL and guide the differential diagnosis; however, histopathologic analysis is required for a definitive diagnosis.