Mast cells (MCs) play an important role in cancer promoting, by producing a large amount of metalloproteinases and thus contributing to the tumor diffusion process, and by secreting prestored mediators such as corticotropin-releasing hormone (CRH), neurotensin (NT), substance P (SP), tryptase, vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF), prostaglandins, and leukotrienes, some of which are known to disrupt the integrity of the BBB, stimulating peritumoral brain edema (PTBE) formation [9,41,43]. The gene discussed is TAC1; the disease is neoplasm.