In addition to correctly identifying the IDH1/IDH2 status of tumors with the common IDH1 p.Arg132His variant, the reported epi-signature also enabled the identification of tumors with less common pathogenic IDH1 and IDH2 mutations, including one tumor with an IDH1 p.Arg132Cys variant and one tumor with an IDH2 p.Arg172Lys variant. Here, IDH2 is linked to neoplasm.