IDH2 and bone neoplasm: The majority of chondrosarcomas, the most common primary malignant bone tumour of adults, harbour single point mutations in the cytosolic isocitrate dehydrogenase type 1 (IDH1; 60% cases) and in the mitochondrial isocitrate dehydrogenase type 2 (IDH2) (10% cases) [76, 77], key enzymes in the tricarboxylic acid cycle [78].