We excluded mutations in other metabolic enzymes in the 27 cartilaginous tumours that were wildtype for IDH, since all tumours were positive for SDHB immunohistochemical staining, suggesting an intact SDH complex and thereby excluding mutations in the different SDH subunits [44] (Additional file 3: Figure S2A; Additional file 4: Table S2). The gene discussed is IDH2; the disease is neoplasm.