Epithelioid Angiomyolipoma of the Kidney Mimicking Renal Cell Carcinoma: A Clinicopathologic Analysis of Cases and Literature Review

Classical renal angiomyolipoma (AML) is a common tumor that, in most cases, follows a benign course and has clearly defined radiologic and histological characteristics. However, rare cases of clinically aggressive or malignant AML, the epithelioid variant of AML (EAML), have been reported. Here, we review the five cases of EAML diagnosed since 2000 at our institution to highlight the spectrum of clinical, radiological and histological characteristics. In all cases, renal lesions seen on computed tomography (CT) were considered as suspicious for renal cell carcinoma (RCC) without tumor extension or metastasis. One of the two patients with definitive tuberous sclerosis complex had a small conventional AML with fat content in the other kidney. Histologically, these tumors can resemble sarcomatoid RCC or high grade RCC. The final diagnosis is established by the presence of perivascular epithelioid cells and immunohistochemistry markers. There was no evidence of local recurrence or metastatic disease found by sonography, CT and magnetic resonance imaging during the follow-up period. EAMLs are capable of aggressive or malignant clinical behavior. Approximately one third of the reported EAMLs show advanced disease; therefore, we recommend that it is important to treat and closely follow-up such cases, similar to that for RCC, because of its malignant potential.