What sort of problem is a brain astrocytoma?

Brain cancer. It is a fairly common type of primary brain cancer. It comes in 4 grades, with grade 1 being better prognosis and grade 4 rapidly progressive. Treatment options exist so consult a cancer doctor.
Cancer. Virually all brain tumors should be considered malignant even though they do not spread outside the brain. Astrocytomas have different grades of aggressiveness and can vary from slow growing for years to rapidly fatal.