In the context of previous literature surrounding molecular prognostic factors in diffuse glioma subsets and the impact of MMR mutations in gliomas and other brain and systemic tumors, this report adds to the body of evidence suggesting that these mutations should be routinely screened for in both primary and recurrent gliomas, particularly IDH-mutant astrocytomas, which can be performed with standard immunohistochemical panels and targeted next-generation sequencing platforms. This evidence concerns the gene MRC1 and astrocytoma (excluding glioblastoma).