Astrocytoma is defined as a tumor composed of astrocytes. It is the most common type of primary brain tumor and is also found throughout the central nervous system. One classification groups astrocytomas according to their histologic appearance and distinguishes pilocytic, protoplasmic, gemistocytic, and fibrillary types. Another classification groups them in order of increasing malignancy as Grade I, Grade II, Grade III, and Grade IV astrocytomas.
Glial tumors may cause patients to develop many symptoms. A more benign type of glioma can occur in younger people and could present as a seizure. Depending on the area of the brain involved, a progressive neurological problem, such as weakness, numbness, or speech problems can develop. Since the more malignant tumors enlarge rapidly, symptoms of increased pressure in the head are common: headache, visual loss, and personality change. Headache is characteristically worse in the morning when awakening. On rare occasions a glial tumor can bleed spontaneously, presenting with an acute neurological deficit of stroke.
The classification of gliomas is based upon the appearance of these tumors under the microscope. This requires a biopsy of tumor tissue and in general is predictive of the behavior of the tumor and the outlook for the patient. Glial tumors are divided into two basic cell types: astrocytomas and oligodendrogliomas. The most common grading system for astrocytomas is the following World Health Organization (WHO) system:
Grade I: Pilocytic Astrocytoma – a group of generally slow-growing astrocytomas, including most fibrillary and pilocytic astrocytomas.
Grade II: Fibrillary Astrocytoma – astrocytomas with slightly more malignant potential than those of Grade I, including astroblastomas and some fibrillary and pilocytic astrocytomas. One classification system includes some anaplastic astrocytomas in this group.
Grade III: Anaplastic Astrocytoma – moderately malignant astrocytomas, sometimes including the less malignant of the gliosblastoma multiforme group.
Grade IV: Glioblastoma Multiforme – astrocytoma that is highly malignant. This group includes only the glioblastoma multiforme type, although some less malignant glioblastomas are sometimes classified as Grade III.
|grade II: fibrillary astrocytoma||grade III: anaplastic astrocytoma||grade IV: glioblastoma multiforme|
Stereotactic radiosurgery may be used to treat gliomas deep within the brain, near sensitive brain regions or when the patient is not a candidate for surgery.