The exclusion of secondary GBMs thus selected against the IDH1-mutant PN tumors, also referred to as the G-CIMP-positive tumors, but the lack of markers for the G-CIMP-negative PN tumors probably also contributed substantially to the lower identification rate of the PN subclass [37], [48], [49]. Here, IDH1 is linked to poikiloderma with neutropenia.