Renal epithelioid angiomyolipoma: MRI findings.

Purpose: To retrospectively analyze the MR imaging presentation of renal epithelioid angiomyolipoma (EAML).

Methods: Retrospective analysis revealed 12 subjects with histologically proven renal EAML who underwent preoperative MRI at our institution between January 2009 and June 2016. Two radiologists reviewed the images in consensus, describing MR imaging features including size, location, growth pattern, signal intensity of tumor, and dynamic enhancement pattern.

Results: Nine women and three men were included. The average maximum tumor diameter was 7.1 cm. Exophytic growth was present in 9/12 cases, mesophytic growth in 2/12, and endophytic growth in 1/12. On T1-weighted images, 2/12 displayed homogeneous isointensity, 1/12 homogeneous hyperintensity, 5/12 heterogeneous hypointensity, and 4/12 heterogeneous hyperintensity. Macroscopic fat was detected in 5/12 cases and microscopic fat in 6/12 cases. On T2-weighted images, 5/12 showed heterogeneous hypointensity, 4/12 heterogeneous hyperintensity, and 3/12 homogeneous hypointensity. On dynamic contrast-enhanced MR images, 7/12 showed a slow washout enhancement pattern, 2/12 a rapid washout pattern, 2/12 progressive enhancement, and 1/12 persistent enhancement. Imaging findings were suggestive of hemorrhage (50%), necrosis (25%), or cystic change (50%) within the tumors. Enlarged vessels were detected in 5/12 cases. One tumor extended into the renal sinus. No metastases were found on the preoperative MR imaging.

Conclusion: Although MRI appearances of renal EAML were various, some MRI characteristics may contribute to suggest the possibility of renal EAML.