GFAP detected in 0/7 grade II, 0/10 grade III, 13/34 grade IV, 1/41 metastasis, 1/25 MS patients, and 1/26 healthy controls. Significant association with grade IV astrocytoma diagnosis.Higher serum levels in grade IV compared to ICM.Grade IV: No correlation to neuroradiological characteristicsPatients with detectable GFAP in serum levels had a longer survival probability (11.3 months) compared to others (5.2 months). Here, GFAP is linked to myeloid sarcoma.