FN1 and glioblastoma: Additionally, we observed CD45+ leukocyte aggregates near lymphatic‐endothelial‐like (LEC‐like) cells in 3 out of 6 glioblastoma samples, typically within or near collagen I/III‐rich ECM containing untensed fibronectin, both in the parenchyma and at the tumor margin (Figure 5).