Multifocal vascular neoplasm with an EWSR1::NFATC2 gene fusion and progression to epithelioid angiosarcoma - a case report.

There is an emerging group of distinct vascular neoplasms with NFATC1/2 fusions, involving bones and soft tissues and often displaying focal epithelioid morphology, variable atypia of endothelial cells, predominantly vasoformative and in some cases focal solid growth. Although they may show aggressive local growth and may recur locally, malignant behaviour has not been documented. We present a case of a 35-year-old woman with multiple vascular neoplasms with a EWSR1::NFATC2 fusion involving the lungs, multiple bones (vertebra, femurs, tibia, pelvis) and probably the liver. The bone lesions were locally aggressive and recurred after surgical treatment. Nine years after the first manifestation, there was progression to an epithelioid angiosarcoma. The patient died 3 months after the diagnosis of epithelioid angiosarcoma with massive lung and liver involvement(metastases). In addition to the EWSR1::NFATC2 fusion, an activating PIK3CA gene mutation was identified in the angiosarcoma but not in the previously diagnosed bone tumours. To the best of our knowledge, this is the first documentation of malignant progression of a vascular neoplasm with NFATC1/2 fusion as well as visceral (lung) involvement.