Malignant Perivascular Epithelioid Cell Tumor Mimicking Renal Cell Carcinoma: A Diagnostic Pitfall

Abstract

Abstract We describe a case of metastatic malignant renal perivascular epithelioid cell tumor in a 56-year-old male. Computed tomography initially revealed bilateral heterogeneous enhancing kidney masses, the right one significantly larger than the left. The patient underwent a right radical nephrectomy. Upon gross examination, the mass was infiltrating into the surrounding fat and had a heterogeneous cut surface with multiple hemorrhagic foci. Histologically, majority of cells were highly atypical with abundant clear cytoplasm, pleomorphic nuclei, and enlarged prominent nucleoli. Extensive lymphovascular invasion was noted. Based on morphology, the diagnosis of renal cell carcinoma, Fuhrman grade 4, with extensive rhabdoid and focal sarcomatoid features was rendered. Follow-up computed tomography demonstrated a hypodense area within the right hepatic lobe, which upon resection showed identical morphology to the renal mass, except for focal areas of prominent epithelioid cells with abundant eosinophilic cytoplasm. Immunohistochemistry of both resection specimens (kidney and liver) demonstrated positive staining for Melan-A, HMB-45, and epithelial membrane antigen, focal positive staining for TFE3, and negative staining for PAX8 and cytokeratin. The initial diagnosis of renal cell carcinoma was amended to malignant epithelioid angiomyolipoma with hepatic metastasis. The diagnosis of angiomyolipoma/perivascular epithelioid cell tumor is particularly problematic owing to the large number of potential mimics. Immunohistochemistry for myomelanocytic differentiation should be considered in the context of kidney lesions with epithelioid and spindled cell morphology.