Novel YAP1‐TFE3 fusion defines a distinct subset of epithelioid hemangioendothelioma

Conventional epithelioid hemangioendotheliomas (EHE) have a distinctive morphologic appearance and are characterized by a recurrent t(1;3) translocation, resulting in a WWTR1-CAMTA1 fusion gene. We have recently encountered a fusion-negative subset characterized by a somewhat different morphology, including focally well-formed vasoformative features, which was further investigated for recurrent genetic abnormalities. Based on a case showing strong transcription factor E3 (TFE3) immunoreactivity, fluorescence in situ hybridization (FISH) analysis for TFE3 gene rearrangement was applied to the index case as well as to nine additional cases, selected through negative WWTR1-CAMTA1 screening. A control group,…