Astrocytomas
Pilocytic Astrocytoma
Pilocytic astrocytomas, which are grade I tumors, are considered benign because they do not invade the surrounding normal brain tissue. These are slow-growing tumors, but can become very large. Pilocytic astrocytomas frequently have cystic portions filled with fluid and a nodule, which is the more solid portion. They are the most commonly diagnosed brain tumor in children aged 15-19. Most pilocytic astrocytomas are located in the cerebellum. The cerebellum is responsible for coordination, so most symptoms of this type of tumor are related to balance or coordination difficulties.
Grade II Astrocytoma
These tumors invade surrounding healthy tissue but grow relatively slowly. This group of tumors includes low-grade astrocytomas and fibrillary or protoplasmic astrocytomas. Mixed gliomas, which contain astrocytoma cells and either oligodendroglioma or ependymoma cells, or both, are commonly graded II or III.
Astrocytomas are the most commonly diagnosed brain tumor in children aged 10-14. Astrocytomas comprise 8% of primary brain tumors.
Anaplastic Astrocytoma
Anaplastic astrocytomas, which are malignant tumors, comprise 4% of primary brain tumors. This type of grade III tumor grows more rapidly than lower grade tumors and tends to invade nearby healthy tissue. Anaplastic astrocytomas recur more frequently than some lower grade tumors, because their tendency to spread into surrounding tissue makes them difficult to completely remove surgically. An anaplastic astrocytoma can be a reoccurrence of a lower grade, previously treated astrocytoma.
Glioblastoma Multiforme
Glioblastoma multiforme, a grade IV tumor, is a malignant astrocytoma that contains areas of dead tumor cells. Gliosarcoma and giant cell glioblastoma are variants of glioblastoma multiforme. Approximately 50% of astrocytomas are glioblastomas.
Glioblastomas typically contain more than one cell type. While one cell type may die off in response to a particular treatment, the other cell types may continue to multiply. This characteristic makes glioblastomas very difficult to treat.
Glioblastomas comprise 23% of primary brain tumors in the U.S., and are the most commonly diagnosed brain tumor in adults aged 45-74. Men are more frequently diagnosed with glioblastoma multiforme than women.