An astrocytoma is a tumor
that arises from astrocyte
s. Astrocytes are star
-shaped (hence the name) cells in the brain that perform many important funtions to enable the neuron
s to perform their functions. They are the most common brain tumors found in children. Astrocytomas can be found anywhere in the brain, but most commonly occur in the cerebellum
Astrocytomas vary wildly in their capacity to causes harm, and in their malignancy. The usual system of classification divides astrocytomas into four grades.
Grade 1 (pilocytic Astrocytoma) tumors generally involve little more than astrocytes growing out of control. They are slow growing, and the function of the cells is not changed. Problems only develop after the tumor has grown to a size at which pressure is exerted on surrounding tissues, and this can cause symptoms. If the tumor becomes large it is normally treated surgically.
Grade 2 astrocytomas involve some abnormality in the astrocytes involved. This can cause problems for surrounding brain tissue. While these tumors do not usually cause death very quickly, radiotherapy is strongly advised, as it more than doubles the five-year survival rate (to above 70%).
Grade 3 (anaplastic astrocytoma) astrocytomas are much more serious. Even with extensive treatment many patients die within a year. The mean survival time for a grade 3 tumor is only 18 months. Cells from a grade 3 tumor behave malignantly. They go through mitosis at a vastly increased rate, and form solid masses of cancerous cells, destroying brain tissue that was previously there. Both radiotherapy and chemotherapy are used to treat these astrocytomas.
Grade 4 (glioblastoma) tumors are very similar to grade 3 tumors, but grow even faster. They are characterised by areas of dead tissue where the tumor has grown faster than the blood supply system can keep up. Many patients die within weeks of a grade 4 astrocytoma diagnosis, and few live longer than a year, even with intensive treatment.
Symptoms of a brain tumor. Symptoms depend upon the size, positioning and malignancy of the tumor.
Diagnosis of brain cancer such as astrocytoma is usually by biopsy. A preliminary scan locates areas of abnormality. The person examining the sample will be looking for increased numbers of astrocytes, many cells undergoing mitosis, and abnormalities in these cells.
Collins medical dictionary