COL4A4 and glioblastoma: Comparable pathologic findings were reported in previous studies, with diffuse GBM thinning in 81% (141/174) of patients with mono-allelic variants in COL4A3/COL4A4, an isolated finding in 54% of patients and accompanied by other findings in 27%, and lamination of the GBM in 7% (12/174) of patients.22