Definition: Oligoastrocytomas are tumors that are a mixture of cells that originated from oligodendrocytes and astrocytes, two types of cells in the brain that support and insulate nerve cells. The World Health Organization classifies oligoastrocytomas as grade II (low-grade) or grade III (anaplastic) based on how quickly the tumor cells are dividing. A grade II oligoastrocytoma can transform to a grade III oligoastrocytoma over time.
Symptoms: Seizures are a common initial symptom of an oligoastrocytoma. Other symptoms depend on the location of the tumor.
Evaluation: Oligoastrocytomas are evaluated with MRI scans.
- Grade II oligoastrocytoma: Surgical biopsy and removal of as much of the tumor as possible without causing significant neurological damage is the first step in the treatment of a grade II oligoastrocytoma. A biopsy may be all that is possible if the tumor is located in a critical area of the brain. Focal fractionated radiation therapy may be considered to control seizures related to the tumor that cannot be controlled with seizure medications. If the tumor recurs, surgical resection, radiation, chemotherapy or all three will be considered.
- Grade III oligoastrocytoma: Surgical biopsy and removal of as much of the tumor as possible without causing significant neurological damage is the first step in the treatment of a grade III oligoastrocytoma. Focal fractionated radiation in combination with chemotherapy are usually started 2 to 4 weeks after surgery. Follow-up: Long-term close follow-up with regular MRI scans is recommended to watch for tumor recurrence, growth, or transformation to a higher grade.