FOSB and fibrosarcoma: At the same time, the complexity of genetically classifying these tumors has increased as a result of the discovery of new fusion transcripts in already well-defined entities, for example, COL1A2-PDGFB, COL6A3-PDGFD, or EMILIN2-PDGFD fusion-positive DFSP, the various NTRK fusions in infantile fibrosarcoma, or the new FOSB fusions in pseudomyogenic hemangioendothelioma.