C3 and brain neoplasm: In the second level, we try to define specific features from each tumour separately to this end, we are indicating four hub genes only in the brain tumours that included GNG2, CXCL8, C3, and PTPN6 with also report three pathways poly-N-acetyllactosamine biosynthetic process, mucin-type O-glycan biosynthesis pathway, and calcium reabsorption pathway specifically for the brain metastasis tumours.