IDH1 and chondroblastic osteosarcoma: The presence of IDH mutations can also be used in differential diagnostic between dedifferentiated CHS and undifferentiated pleomorphic sarcoma of bone (UPS) [78] or high-grade CHS and chondroblastic osteosarcoma [60], where UPS and chondroblastic osteosarcoma lack IDH1/2 mutations.