Epithelioid Angiomyolipoma With Prominent Papillary Architecture Mimicking Renal Cell Carcinoma: A Case Report

Renal epithelioid angiomyolipoma (EAML) (epithelioid PEComa of the kidney), is a rare subtype of renal angiomyolipoma with the potential for aggressive behavior and a known diagnostically challenging entity. We present a renal EAML with unusual papillary architecture and tumor cells with abundant eosinophilic cytoplasm and cherry-red nucleoli with perinucleolar halos, strongly mimicking a fumarate hydratase (FH) deficient renal cell carcinoma (RCC). We herein report our findings and discuss the morphologic, immunohistochemical, and molecular pitfalls to consider in the differential of EAML, including with FH-deficient RCC and more recently described entities: TFEB-amplified RCC and other renal tumors with alterations in TSC1/2. Novel findings in this tumor include papillary morphology and a novel telomerase reverse transcriptase promoter rearrangement, which has not been previously reported in EAML.

Automated summary

Renal epithelioid angiomyolipoma (EAML) is a rare subtype of renal angiomyolipoma with aggressive behavior and diagnostic challenges. This report describes a renal EAML with unusual papillary architecture and tumor cells resembling FH-deficient RCC. The study highlights the morphologic, immunohistochemical, and molecular aspects of EAML, including differential diagnosis with FH-deficient RCC, TFEB-amplified RCC, and renal tumors with TSC1/2 alterations. Novel findings in this case include papillary morphology and a previously unreported telomerase reverse transcriptase promoter rearrangement.