Table 1. Percentage of mutations of particular genes in primary and secondary glioblastomas.

Mutated genes	Primary glioblastoma	Secondary glioblastoma	References
EGFR	36%	8%	11
p16INK4a	31%	19%	11
PTEN	25%	4%	11
TP53	30%	50%	11
IDH1	5%	80%	14, 15, 16

The difference in the occurrence of certain mutations between the two types of glioblastomas allowed its molecular classification. Whereas primary glioblastoma is mainly characterized by mutations in EGFR, p16INK4a and PTEN, secondary glioblastoma harbors TP53 and IDH1 mutations.