The World Health Organization (WHO) uses a grading system regarding the level of aggression of astrocytomas. This is simply the most commonly used system, as other ones are also in place for those who do not prefer to use the standards in the WHO's system. This particular system grades the tumors on a scale of 1 to 4, where 4 is the most aggressive form. The following are the classifications, with an example of each kind:
Grade 1 - pilocytic
Grade 2 - diffuse / low-grade
Grade 3 - anaplastic / malignant
Grade 4 - glioblastoma multiforme
This type is most often found in children, and sometimes has the prefix of "juvenile" added. Typically, it is considered as a benign childhood tumor. Frequently, this type is cystic, and well-circumscribed if solid.
This is one form of the low-grade classification, as is pleomorphic xanthoastrocytoma, and sometimes the aforementioned pilocytic type is listed in this category. In many cases, radiation therapy is the first method of treatment considered for a low-grade type.
Anaplasia is a characteristic of malignant tumors (or neoplasms). Therefore, this form is considered, by name, to be malignant in nature.
The most aggressive form of astrocytomas, a glioblastoma multiform (GBM for short) is also the most common kind of primary brain tumor (one which originates in the brain). There are two variants: gliosarcoma and giant cell glioblastoma.
To read more general information on astrocytomas, visit the home page. You can also go right to a particular page discussing possible symptoms.