IDH2 and Cowden syndrome 1: Previously, we reported results from a small cohort of patients with central cartilaginous tumours (n = 29 CS) and showed that IDH1‐ and IDH2‐mutant molecules (ctDNA) could be detected in plasma from all patients with CS G3 and dedifferentiated CS, in approximately 50% of those with G2 disease and never in patients diagnosed with well‐differentiated cartilaginous tumours [23].