Diffuse low grade glioma MAPK pathway altered

Last revised by Joshua Yap on 20 Jul 2022

Diffuse low-grade glioma, MAPK pathway-altered is a novel tumor type included in the 5th Edition (2021) of the WHO brain tumor classification 1.

Several genetic mutations were recognized in low-grade IDH-wt/H3-wt brain diffuse gliomas occurring in children and adolescents, such as BRAF V600E mutation, FGFR alteration, and MYB/MYBL1 arrangement 2-7. Except for the last, all the above-mentioned mutations determine a direct up-regulation of the RAS/MAPK pathway and therefore these low-grade gliomas are likely expressions of a "one-pathway disease" 7. Moreover, it is important to emphasize that many other genetic alterations, such as NF1 tumor suppressor gene mutation, affect the RAS/MAPK pathway 7. Therefore in 2019, the cIMPACT-now committee proposed to classify and distinguish low-grade pediatric diffuse gliomas on the basis of these genetic mutations 8.

The 5th edition (2021) of the WHO brain tumor classification introduced diffuse low-grade glioma MAPK pathway-altered in the family of "pediatric low-grade" diffuse gliomas 1.

The term diffuse low-grade glioma MAPK pathway-altered encompasses a broad spectrum of histological features, including astrocytic, oligodendroglial, or mixed morphology 1, 7. Therefore, the correct identification of diffuse low-grade glioma MAPK pathway-altered requires molecular characterization and in particular the detection of BRAF or FGFR mutations 1, 7.

At the time of writing (c. 2022), there are few published radiological descriptions of brain tumors specifically falling into the category of diffuse low-grade gliomas MAPK pathway-altered. In general, it is possible to assume that their appearance is similar to the other diffuse low-grade gliomas belonging to the same family. It may appear as a heterogenous enhancing mass with cystic changes 9.

Specific data on the prognosis and treatment of diffuse low-grade glioma MAPK pathway-altered are not yet available. One may speculate that, as with other tumors in the same family, the prognosis is good, although the possibility of surgical resection depends on the location.

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