====== Diffuse astrocytoma differential diagnosis ======

[[Reactive gliosis]] is a response of [[glia]]l [[tissue]] to different types of [[injury]] such as [[brain abscess]], [[trauma]], [[hemorrhage]], or even neoplastic process. In some circumstances, especially when the tissue [[biopsy]] is small, there may be difficult to discriminate this reactive condition with low-grade [[diffuse astrocytoma]] (World Health Organization [WHO] grade II) by conventional [[hematoxylin]] and [[eosin]] (H&E) slides, so some immunohistochemical and [[molecular marker]]s have been introduced for this [[differential diagnosis]]. One of the important aspects of the updated WHO classification in 2016 has been dividing some of the glial tumors according to [[IDH1]] (isocitrate dehydrogenase 1) mutation.

The most commonly used markers to differentiate astrocytoma from [[astrocytosis]] are immunohistochemical stains for glial fibrillary acid protein (GFAP), proliferation markers (e.g. Ki-67), and p53.

In a study, Geramizadeh et al. tried to evaluate IDH1 and [[P53]] mutation by [[immunohistochemistry]] as a simple and highly specific, and sensitive method to differentiate low-grade astrocytoma and reactive gliosis.

For 5 years (2013-2018), 50 cases of clinically documented reactive gliosis and 50 cases of low-grade astrocytoma were evaluated for the presence or absence of IDH1 and P53 mutation by immunohistochemistry.

Isocitrate dehydrogenase 1 was positive in 92% and 4% of the astrocytoma and reactive gliosis cases and P53 was positive in 90% and 4% of the cases with the final diagnosis of astrocytoma and reactive gliosis, respectively.

The combination of P53 and IDH1 as an immunohistochemical panel showed a specificity of 96% and sensitivity of 91% for differential diagnosis of reactive [[gliosis]] and [[low-grade astrocytoma]]. These 2 markers can be extremely helpful for this differential diagnosis
((Geramizadeh B, Kohandel-Shirazi M, Soltani A. A Simple Panel of IDH1 and P53 in Differential Diagnosis Between Low-Grade Astrocytoma and Reactive Gliosis. Clin Pathol. 2021 Feb 11;14:2632010X20986168. doi: 10.1177/2632010X20986168. PMID: 33634261; PMCID: PMC7887675.)).