ABSTRACT
Objective:To investigate the clinicopathological features and differential diagnosis of 2 patients with renal epithelioid angiomyolipoma (AML), representing 5.4 % of a series of 37 patients undergoing biopsy for renal tumors. Methods:The histopathological, immunohistochemical and clinical characteristics of renal epithelioid angiomyolipoma were studied by immunohistochemical stain for melanoma marker (HMB45), (Pan)melanoma marker Ab-1,cytokeratin (CK), smooth muscle actin (SMA), epithelial membrane antigen (EMA),vimentin (Vim), p53, proliferating cell nuclear antigen(PCNA), Ki67 antigen. Results:Two patients,aged 31 and 39,were alive for 8 and 10 months,respectively.Microscopically, both tumors were mainly made up of diffuse sheets of epithelioid cells and scattered thick-walled blood vessels, necrosis was account for up to 30% of the mass. The epithelioid cells had huge, extremely pleomorphic nuclei with abundant eosinophilic cytoplasm. Scattered tumor giant cells with prominent nuclei were also seen. The epithelioid AML regions of these tumors were immunoreactive for HMB45, (Pan)melanoma marker Ab-1, SMA, Vim and PCNA. Neither atypical epithelioid cells nor typical AML cells were immunoreactive for cytokeratin (CK) and epithelial membrane antigen (EMA).Conclusion: The results of this study suggested that the renal epithelioid AML was a mild malignant tumor before distant metastases. The differential diagnosis between renal malignant AML and sarcomatoid renal cell carcinoma was established by immunohistochemical findings.