Monarch Disease Ontology entry MONDO_0016683 (gliomatosis cerebri) is a diffuse glial tumor which infiltrates the brain extensively, involving more than two lobes. It is frequently bilateral and often extends to the infratentorial structures, even to the spinal cord. It is probably of astrocytic origin, although GFAP expression may be scant or absent. (Adapted from WHO.). Also known as: astrocytosis cerebri, gliomatosis, gliomatosis cerebri (morphologic abnormality).