Angiomyolipoma of the kidney: clinicopathological and immunohistochemical study

Abstract

Overview: Although angiomyolipoma (AML) is a relatively rare entity, it is the most common benign mesenchymal neoplasm of the kidney.

The aim of this study: To highlight the clinicopathological characteristics of AML and to assess the role of Human Melanoma Black-45 (HMB-45), Melan-A, smooth muscle actin (SMA), S-100 and cytokeratin in its diagnosis.

Materials and methods: The study included 15 cases of AML. Clinical and radiological data were retrieved from the archival files and all cases were subjected to a histopathological evaluation as well as immunohistochemical staining for HMB-45, Melan-A, SMA, S-100, and cytokeratin.

Results: AML was more common in females (female:male = 4:1), the mean age was 53.9 ± 6.45 years. 60% of patients were symptomatic while the remaining 40% were asymptomatic. A statistically significant relationship was found between size of the tumor and the presence of the symptoms (P = 0.02). Patients with tumor size less than 4 cm were asymptomatic, while those with tumor size larger than 4 cm had different symptoms. Thirteen cases were classic AML, while 2 cases were epithelioid AML. Classic AML demonstrated admixture of fatty tissue, thick-walled blood vessels, and smooth muscle, while epithelioid AML was composed mainly of epithelioid cells and contained no fat. HMB-45 was positive in all cases of AML (100%), Melan-A was positive in 13/15 (87%) while SMA was positive in 11/15 (73%) of AML with variable staining intensity. All cases of AML were negative for S-100 and cytokeratin.

Conclusion: AMLs have characteristic clinicopathological and immunohistochemical features and their recognition is crucial for proper diagnosis and treatment.

Keywords: AML; Angiomyolipoma; CT; EAMLs; HMB-45; HPF; Human Melanoma Black; MRI; Magnetic Resonance Imaging; Melan-A; PEC; PEComas; SMA; Smooth muscle actin; TSC; U/S; WHO; World Health Organization; angiomyolipoma; computed tomography; epithelioid angiomyolipomas; high power fieldpa; perivascular epithelioid cell; perivascular epithelioid cell tumors; smooth muscle actin; tuberous sclerosis complex; ultrasound.