This alludes to possible errors in the histopathological assessment of the tumor molecular status originating from variability in cutoff values used to determine IDH status in immunohistochemistry (IHC) evaluations,42 heterogeneity of staining in IHC leading to partial uptakes,43 or heterogeneity in samples where only a fraction of tumor cells have IDH1-R132H expression.44 This evidence concerns the gene IDH1 and neoplasm.