الفهرس 
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Abstract
Glioma is the most common CNS neoplasm that originates from glial cells. In the past, these diffuse gliomas were classified into different subtypes and grades based on histopathology. Recently, gliomas are classified based on molecular and genetic markers. These advances have more specific prognostic and therapeutic benefits for patients with gliomas. In addition to molecular and genetic markers, gliomas are classified in four grades based on the degree of proliferation indicated by the mitotic index and the presence or absence of necrosis.
IDH plays a key role in the Krebs cycle and cellular homoeostasis. The mutation of IDH1 is the most frequent genomic alteration found in gliomas, affecting 40% of these tumors and is one of the earliest alterations occurring in development of glioma. The WHO classification of CNS (2016) classified diffusely infiltrating gliomas based on IDH-mutation status, whilst the recent WHO classification (2021) defines a distinct family of tumors upon this genetic alteration. Generally, IDH-mutated glioma has a better outcome than IDH wild-type.
DNA mismatch repair (MMR) is a system to identify and repair mismatched nucleotides to guarantee genomic stability and integrity. Four key genes for DNA mismatch repair which are MSH2, MSH6, MLH1, and PMS2. These main proteins are usually identified through immunohistochemical analysis in clinical settings. Immunohistochemical loss of at least one MMR protein expression was reported by other studies with the hypermutation profile in glioma patients. PMS2 could not be statistically evaluated as all included cases showed expression positivity. There was a highly significant association between both MSH6 and MSH2 expression and patient survival, while there was not with MLH1 expression
Immunohistochemistry is a low cost and beneficial tool for evaluation of IDH1 and MMR genes status for patients of gliomas. So, for better prediction of outcome of patients of gliomas, it is highly recommended to assess and evaluate patients’ survival based on these genes’ status.