CD14 and glioblastoma: Firstly, for the early diagnosis of tumors, as EpCAM is widely expressed on the surface of CTCs derived from cancer cells, most CTCs detect cells targeting EpCAM, but EpCAM is not present in GBM cells.263 Thus, it has been suggested that circulating brain tumor cells are detected by GBM-specific expression of CD14, CD16, etc.264 In comparison to blood, CTCs in the cerebrospinal fluid are more readily identifiable and distinguishable from other cells,265 which may result from the presence of the blood-brain barrier and the more complex cellular composition of blood.