Based upon molecular analyses (methylation profiling and fusion gene analysis), in over 50% of our cases, the initial diagnosis was changed into Ewing sarcoma, sarcoma with BCOR alteration, mesenchymal chondrosarcoma, and SEF, emphasizing overlapping clinical, radiological, and pathological features and implicating possible inappropriate treatment for a subset of patients. This evidence concerns the gene BCOR and mesenchymal chondrosarcoma.