Renal angiomyolipoma (AML) is a rare benign neoplasm of mesenchymal origin. AML incidence varies from 0.3 to 5%, while women suffer four times more often than men. In most cases, renal AML measures less than 4 cm, is asymptomatic and detected accidentally with computed tomography or ultrasound. A histological variant of AML need to be verified to choose management strategy and reduce the risk of complications. Histological and immunohistochemical assessment of biopsy and surgical specimens has an essential diagnostic value in determining the type and subtypes of renal neoplasms and the risk of malignancy. The study aimed to investigate pathomorphological and prognostic features (immunohistochemical characteristics) of renal AML.
Materials and methods. Patients (n=42) with CT-detected renal neoplasms underwent partial nephrectomy. The majority (n=34) of patients was admitted to the hospital urgently, often without symptoms (n=23). The surgical specimens studied were examined using light microscopy and immunohistochemistry analysis with primary mouse monoclonal antibodies to HMB-45, Melan-A, α-SMA, S-100 and SC (Novocastra, UK).
Results. All specimens showed morphological characteristics typical of AML and a positive response to antibodies against HMB-45 (ve +/3; 99.6±0.3%), Melan-A (ve + / 2, 89.6±4.3%) and SMA (ve + 2; 70.1±2.9%) and exhibited no staining with antibodies against S-100 and SK. Conclusion. Morphological study of renal AML shows that the tumor is benign, therefore partial nephrectomy, in our opinion, should be considered as an alternative to radical nephrectomy, including for sporadic giant renal AML.

Keywords: renal angiomyolipoma, diagnosis of renal angiomyolipoma, HMB-45, Melan-A, α-SMA