TABLE 2.

Testing Recommendations for Diffuse Gliomas^a

Tests	Recommended Applications
IDH1\IDH2 gene mutational status	All diffuse gliomas As needed for cases of histologic mimics of diffuse gliomas
ATRX immunohistochemistry	As needed in IDH mutant diffuse gliomas to define oligodendroglioma vs astrocytoma lineage
H3F3A K27M immunohistochemistry	IDH wild-type diffuse gliomas in younger patients with midline lesions
BRAF (V600E; c.1799T>A) gene mutational analysis	Differentiating selected low-grade gliomas (extracerebellar pilocytic astrocytomas, gangliogliomas, and pleomorphic xanthoastrocytomas) from diffuse gliomas Suspected cases of epithelioid glioblastoma
1p/19q codeletion analysis (FISH or LOH)	All IDH mutant diffuse gliomas
EGFR FISH	Problematic diffuse glioma cases where diagnosis of primary glioblastoma is suspected
MGMT promoter methylation	All anaplastic (WHO grades III and IV) diffuse gliomas

Abbreviations: EGFR, epidermal growth factor receptor; FISH, fluorescence in situ hybridization; LOH, loss of heterozygosity; WHO, World Health Organization.

^aIn cases where unequivocal astrocytic differentiation has been demonstrated by other ancillary tests (ATRX loss\mutation, TP53 mutation) assessment of 1p/19q status may not be necessary.