CHI3L1 and glioblastoma: Briefly, classical glioblastomas show a high expression of EGFR while mesenchymal glioblastomas show a high expression of mesenchymal and astrocytic markers (e.g., YKL40, CD44 and MERTK) and deletion of NF1. The expression of markers related to oligodendrocytic and proneural development (e.g., OLIG2, PDGFRA and TCF4) is increased in proneural glioblastomas.