As it has been widely reported that overexpression of CD99 could increase the migration and invasiveness of GBM cells (Seol et al., 2012; Cardoso et al., 2019), we deduced that although CD99 and other invasion-associated PCGs play key roles in regulating tumor cell invasion, their mediated mechanisms were distinct and redundant, resulting in their mutually exclusive expression patterns. This evidence concerns the gene CD99 and glioblastoma.