Which statement accurately differentiates reactive gliosis from a glioma?

• A. Reactive gliosis is a neoplastic process with invasion
• B. Reactive gliosis is a non-neoplastic astrocytic response to injury
• C. Glioma is not infiltrative
• D. Reactive gliosis lacks GFAP expression

Answer: (B)

Differentiating reactive gliosis from a glioma hinges on whether the change is neoplastic or a reactive response. Reactive gliosis is an astrocytic reaction to CNS injury, with astrocyte hypertrophy and proliferation that creates a glial scar; it is a non-neoplastic process, not a tumor. Gliomas, on the other hand, are neoplastic glial tumors arising from astrocytes or oligodendrocyte lineage and characteristically show clonal proliferation with infiltrative growth into surrounding brain tissue. GFAP, a marker for astrocytes, is upregulated in reactive astrocytes, so reactive gliosis does express GFAP. Infiltration is typical of gliomas but not a feature of reactive gliosis. Therefore the statement that reactive gliosis is a non-neoplastic astrocytic response to injury best differentiates it from a glioma.