Hemangioblastoma of the central nervous system is a benign tumor (WHO grae I) that is typically cystic and can occur throughout the central nervous system. It is a tumor composed of hemangioblasts, a type of stem cell that normally give rise to blood vessels or blood cells. Its name breaks down to Greek roots as follows: Haema (blood), angeion (vessel), blastos (embryonic), oma (tumor).