We screened 42 primary glioblastomas (WHO grade IV) for mutations in the 14 exons of HOT. Four of these tumors were known from previous analysis to carry IDH1 R132H mutations, but none carried mutations in IDH2, IDH3, L2HGDH or D2HGDH [47]. The gene discussed is IDH1; the disease is glioblastoma.