Table 1.

Most common brain cancers ordered by type, salient molecular aberrations, and salient microenvironmental or histological features displayed.

Cancer	Molecular classes	Salient molecular aberrations	Salient microenvironmental and/or histological features
PRIMARY BRAIN CANCERS
Pediatric
Medulloblastoma (18)
	WNT	Increased WNT signaling	Fenestrated vasculature enabling access of chemotherapy (19)
	SHH	Increased SHH signaling	Intact BBB that restricts access of chemotherapy (19)
	3	MYC amplification	Higher proportion of PD-1+ CD8+ T cells (20)
	4	CDK4 and MYCN amplification
Adult
Glioma
HIGH GRADE (WHO grade 4)
Glioblastoma (21–23)
	IDHwt
	MES	NF-1 loss	Higher macrophage infiltrate (23–26). More CD4 T cells and neutrophils (23). Higher PD-L1 expression (23).
	CL	EGFR gain and PTEN loss
	PN	PDGFRA gain	Associated with lower levels of PD-L1 (23)
	IDHmut		Blunted T cell abundance and activation (27). Reduced neutrophils (28) and downregulation of NKG2D (29)
	PN	IDH mutations
LOW GRADE (WHO grade 1–3)
Astrocytomas		TP53 and ATRX mutations (30)	Microenvironmental signature enriched in macrophage/microglia-associated genes (31)
Oligodendrogliomas		TERT promoter mutations and 1p/19q co-deletion (30)	Microenvironmental signature enriched in neuron-associated genes (31)
METASTATIC BRAIN CANCERS
Breast cancer		EGFR gain (only HER2+ tumors)
Melanoma		BRAF mutations	Stat3+ pro-tumorigenic astrocytes (32). Communication between astrocytes and tumor cells by extracellular vesicles (33) or cx43-dependent gap junctions (34)
Lung cancer		KRAS mutations, ALK translocation, EGFR amplification