EWSR1 and mesenchymal chondrosarcoma: Similarly, osteosarcoma comprised the most common OSTJS histotype in the pediatric population (8, 53.3%), followed by Ewing sarcoma (4, 26.7%) and 1 each (6.7%) of TFCP2::EWSR1-rearranged rhabdomyosarcoma, mesenchymal chondrosarcoma, and alveolar soft part sarcoma.