IDH1 and chondrosarcoma: In the last decade, recurrent heterozygous hotspot mutations in the arginine residues of the isocitrate dehydrogenase 1 and −2 (IDH1 and IDH2) genes (p.R132 and p.R140/p.R172, respectively) were identified in enchondroma (87%), central conventional chondrosarcoma (~50%), and dedifferentiated chondrosarcoma (>80%) [7,8,9,10].