PECAM1 and myeloid sarcoma: Upon chronic inflammation in MS, pro-inflammatory cytokines such as IFN-γ, IL-17, and IL-1β released by immune cells mediate the breaching of the BBB by upregulation of adhesion molecules (ICAM-1, VCAM-1, E-selectin, and PECAM-1), and loss of junctional integrity [8].