MKI67 and central nervous system cancer: Interestingly, Ki67, a well‐known proliferation marker, was expressed at higher levels in BrMs (55%) than in gliomas (30%), demonstrating a greater tendency of proliferation for BrM after colonizing the brain (Figure 4B; Figure S9, Supporting Information), which aligned with our previous study.[18] The validity of these IHC markers for discriminating BrM from glioma was also confirmed in our proteomic data (Figure 4C; Figure S9, Supporting Information).