Perivascular Epithelioid Cell Tumor of the Lung With a Novel <i>YAP1::TFE3</i> Fusion

Perivascular epithelioid cell tumor (PEComa) belongs to a family of rare mesenchymal neoplasms that share characteristic morphologic, immunohistochemical and molecular findings. In this report, we provide a detailed clinicopathological characterization of a PEComa incidentally discovered in the right lung of a 53-year-old woman. This tumor with epithelioid cell morphology and myomelanocytic differentiation demonstrated a <i>TFE3::YAP1</i> fusion by targeted RNA sequencing. While a subset of PEComas shows <i>TFE3</i> rearrangements, fusion with <i>YAP1</i> has not been systematically documented in this entity. Clear cell stromal tumor of the lung and epithelioid hemangioendothelioma characteristically display the <i>TFE3::YAP1</i> fusion; however, as currently defined, both lack myomelanocytic features. Here, we describe a novel <i>TFE3</i> fusion partner that further expands the spectrum of molecular alterations seen in PEComa.