Renal epithelioid angiomyolipoma: a malignant disease

Background: Renal angiomyolipomas are recognized as clonal neoplasms with clonal chromosomal aberrations and a common progenitor cell, the perivascular epithelial cell (PEC). The epithelioid variant is a recently identified entity, characterized by predominance of PEC and a unique morphologic and immunohistochemical profile. There is accumulating evidence suggesting that renal epithelioid angiomyolipoma (REA) is a malignant disease. Methods: We searched the literature for descriptions of clinical behavior of REA. A Pubmed search was performed using the following key words: angiomyolipoma, epithelioid, perivascular epithelial cell or/and renal tumors. We reviewed a case of fatal REA at our institution. A pathologist reviewed slides to confirm the diagnosis. Results: Upon review of 140 articles, 37 eligible articles were found including 10 articles describing the clinical course of REA. Almost all of the patients described, for whom there was a follow-up available, died of neoplastic progression of the disease, with liver, lung and bone metastases. Four cases were reclassified after retrospective pathology review, and they were fatal. Three of these had been misdiagnosed as renal cell carcinoma (RCC), while 1 was diagnosed as classic angiomyolipoma. Conclusion: Unlike commonly benign classic angiomyolipoma, REA behaves aggressively. It is crucial for the clinician to be aware of and identify this epithelioid variant as a malignant disease. It should be carefully differentiated from RCC. Resection alone may not be curative, and adjuvant therapy should be considered. A multimodality treatment approach needs to be explored for this newly recognized malignant variant renal angiomyolipoma.