Although FOSB-rearranged EH do not show significant morphologic overlap with SERPINE1-FOSB fusion-positive pseudomyogenic hemangioendothelioma, FOSB oncogenic activation is emerging as an important event in these benign and intermediate groups of vascular tumors.
Recurrent SERPINE1-FOSB gene fusions have been reported as the hallmark genetic abnormality in PHE, however, in our experience, a number of cases with typical histology lack this genetic abnormality.
We previously identified characteristic FOSB expression in pseudomyogenic hemangioendothelioma (PHE) with a specific SERPINE1-FOSB fusion, revealing the usefulness of FOSB immunohistochemistry in the differential diagnosis of PHE and its mimics.
Diagnosis of known sarcoma fusions and novel fusion partners by targeted RNA sequencing with identification of a recurrent ACTB-FOSB fusion in pseudomyogenic hemangioendothelioma.
Interestingly, in FOSB overexpressing cells, telatinib specifically affected PDGFRA, FLT1, and FLT4 signaling and downregulated SERPINE1, thereby affecting the self-regulation of the fusion gene.<b>Conclusions:</b> We provide a biological substantiation of a complete clinical remission that was seen in a patient with PHE, showing that telatinib indirectly interferes with the self-regulated expression of the fusion product.