Renal angiomyolipomas: Typical and atypical features on computed tomography and magnetic resonance imaging

Figure 5 Hyperattenuating angiomyolipoma. A 9-year-old girl with a left renal mass suggesting Wilms’ tumor, and biopsy demonstrated angiomyolipoma. A: Axial, sagittal and coronal planes of a contrast-enhanced computed tomography image with a hyperattenuating renal mass without a recognizable fat component (white arrows); B: Macroscopic appearance of the tumor; C: Positive Human Melanoma Black 45 (HMB-45) staining in the cytoplasm of perivascular cells of large vessels was also observed (black arrows). The anti-HMB-45 antibody is a monoclonal antibody that reacts with an antigen present in melanocytic tumors and is nonreactive to most nonmelanoma human malignancies, with some notable exceptions, among which are perivascular epithelioid cell tumors; D: Hematoxylin-eosin staining showing mostly spindle-shaped perivascular cells (orange arrows).