Orthotopic PDXs of GBM have been shown to preserve tumor morphology, invasion patterns, and critical molecular aberrations, such as alterations of TERT, EGFR, PTEN, TP53, BRAF, and IDH1. On the contrary, necrosis and microvascular proliferation seem to be lost upon engraftment, as is the case for some molecular alterations, including PDGFRA amplification [163]. This evidence concerns the gene TERT and glioblastoma.