IDH1 and glioblastoma: A multivariate model has shown that, in the case of a negative R132H-IDH immunohistochemistry in a primary glioblastoma, the probability to have an alternative IDH mutation is <6% in a 50-year old patient and <1% in patients older than 54, and, pragmatically, even in the absence of IDH sequencing, the labelling of such patients as “IDH-wildtype” is reasonable35.