These diagnoses were confirmed by fusion gene analysis (mRNA sequencing (targeted or whole transcriptome sequencing)), revealing an EWSR1::FLI1 (ex11::ex5 and ex8::ex9) in two out of three Ewing sarcomas, a KMT2D::BCOR (ex43::ex7) and a CCNB3::BCOR (ex15::ex6) in the two sarcomas with BCOR alteration, a HEY1::NCOA2 (ex4::ex14) in two out of the three mesenchymal chondrosarcomas, and a FUS::CREBL3 (ex7::ex5) in one out of the two SEFs. The gene discussed is EWSR1; the disease is Ewing sarcoma.