Hemangioblastomas can cause an abnormally high number of red blood cells in the bloodstream due to ectopic production of the hormone erythropoietin as a paraneoplastic syndrome .
The tumors usually are well demarcated from the surrounding brain or spinal cord, but this border of separation does not contain any particular membrane or capsule. The surgical approach must be wide enough to avoid compression of the healthy tissues during retraction. Thorough evaluation of preoperative imaging studies is the key to the safest possible exposure of the tumor. In addition to MRI and CT scans, review the angiography findings to identify the principal blood supply to the tumor mass.