Genetically, two main groups of chondrosarcomas exist: central chondrosarcomas, characterized by mutations in the isocitrate dehydrogenase genes IDH1 and IDH2, and secondary peripheral chondrosarcomas, characterized by alterations in the exostosin glycosyltransferase 1 (EXT1) and 2 (EXT2) genes. The gene discussed is EXT2; the disease is chondrosarcoma.