IDH1 and neoplasm: As the biology and clinical outcome of such an unusual tumor remains poorly understood to date, it may be best to classify such these tumors as “not elsewhere classified” according to cIMPACT-NOW update 1.15 In the unusual setting of loss of ATRX staining in tumor cells in an IDH-wildtype, hemispheric tumor, we recommend H3K27M testing to identify more of such cases for further prognostic stratification.