Amary and Pansuriya pioneering works show that IDH mutations in mesenchymal tumors: 1- are prevalent in cartilaginous tumors rather than in other connective tissue sarcomas; 2- are present in 80% of benign enchondromas and in almost half of conventional chondrosarcomas; 3- occur early in the tumorigenesis; 4- both local and distant recurrences of central conventional chondrosarcoma maintain the same IDH mutational status of the primary lesion; 5- are almost always present in enchondromas of Ollier and Maffuci syndromes [21, 22, 38]. The gene discussed is IDH2; the disease is chondrogenic neoplasm.