Tumor-associated primo vascular system is derived from xenograft, not host

► We demonstrate existence of Primo Vascular System (PVS) in mouse xenograft model. ► We demonstrate PVS as 3rd compartment of vascular system and of tumor origin. ► We characterize first time histological components and nervous tissue in PVS. ► We demonstrate for the first time presence of xenografted-tumor cells in the PVS. ► We show cells present in the tumor-associate PVS have stem cell characteristics.