ASPSCR1: TFE3 Fusion‐Positive Epithelioid Angiomyolipoma/PEComa Lacking Melanocytic Markers: A Case Report
Yuka Kondo, Yoji Nagashima, Kenji Zennami, Megumi Sato, Sayaka Sumiyoshi, Akihiko Sugimoto, Madoka Isomura, Kiyoshi Takahara, Sachiko MinamiguchiABSTRACT
Introduction
Epithelioid angiomyolipoma is a rare perivascular epithelioid cell tumor subtype with malignant potential. Its morphology mimics renal cell carcinoma, posing diagnostic challenges. Half of these cases harbor TSC1 / TSC2 alterations, and a small subset features TFE3 rearrangements, mutually exclusive of TSC mutations. Recently, “perivascular epithelioid cell tumor‐like neoplasms” with ASPSCR1::TFE3 fusion lacking melanocytic markers were described.
Case Presentation
A 25‐year‐old woman presented with a 4.5‐cm renal mass. Biopsy suggested TFE3 ‐rearranged renal cell carcinoma because of diffuse TFE3 positivity and no HMB45 immunoreactivity. Postoperatively, despite a complete lack of melanocytic markers, the tumor was diagnosed as TFE3 ‐rearranged epithelioid angiomyolipoma based on its epithelioid morphology and PAX8 negativity, including a retrospective biopsy study. Fluorescence in situ hybridization confirmed ASPSCR1::TFE3 fusion, suggesting this rare, newly recognized entity.
Conclusion
TFE3 ‐rearranged epithelioid angiomyolipoma can lack melanocytic markers. PAX8 immunohistochemistry and genetic testing help distinguish this potentially aggressive tumor from renal cell carcinoma and TSC ‐mutated subtypes.