Examples include differentiating between local tumour recurrence and secondary tumours in head and neck squamous cell carcinoma by sequence analysis of early tumour driver genes such as TP53 [15] or the identification of clinically relevant groups of gliomas for diagnosis, prognosis and predictive testing by determining the presence or absence of TERT promoter mutations, IDH1/IDH2 mutations and 1p/19q co-deletion [16]. The gene discussed is IDH2; the disease is neoplasm.