Childhood astrocytomas fall under the general category of central nervous system (brain and spinal cord) tumors in children. Astrocytomas are not common in children; nonetheless they do represent the second most frequent type of cancer found in children under the age of fifteen.
About 1,200 to 1,500 children per year in the United States develop new brain tumors. Worldwide, over 40,000 children are so diagnosed each year. A few types of brain cancer occur most commonly in boys, such as PNET (primitive neuroectodermal tumors). But astrocytomas are evenly divided among boys and girls. About 20 percent occur in children under the age of two.
Astrocytomas represent about 10 percent of all brain tumors. They can be either slow or fast growing (low or high-grade). Some astrocytomas have a low degree of malignancy or can be even classified as benign, whereas others are very aggressive. Hypothalamic/thalamic astrocytomas fall under the category of low grade gliomas.
The connective (supporting) tissue of the brain is composed of cells called glial cells. Astrocytes are star-shaped cells that are part of the glial (connective) tissue of the brain. When they become malignant, astrocytes form a tumor called an astrocytoma (the suffix 'oma' is the medical term for a cancer). Because they are associated with the glial tissue, astrocytomas are grouped with the gliomas, cancers of the connective tissue of the brain. Overall, astrocytomas represent 13 percent of all brain tumors (while glioblastoma multiforme - see below - represents another 23 percent).
Astrocytomas can be classified according to whereabouts in the brain they develop. Hence cerebellar astrocytomas (those found in the brain stem, or cerebellum) and cerebral astrocytomas (found in the cerebrum, the main part of the brain). Cerebellar astrocytomas are more commonly found in children; cerebral tumors are more typical of adults.
The thalamus is the area of the brain concerned with the detection of body temperature, the discernment of pain. The hypothalamus is the area principally concerned with the hormonal regulation of sleep, appetite and body temperature. Astrocytomas of the thalamus and hypothalamus are sometimes termed suprasellar astrocytomas ('supra' being the medical term for 'above' and 'sellar' referring to the anatomical area of the inside of the skull above which the thalamus and hypothalamus are located).
Suprasellar astrocytomas tend to be of the pilocytic astrocytoma or fibrillary astrocytoma type. Because these are relatively low-grade, slow-growing tumors there are often few dramatic symptoms. Symptoms develop over a long period, and tend to be vague - headache, vomiting, fatigue are all commonly found in association with astrocytomas of this type, but since those symptoms are common childhood ailments they don't tend to arouse suspicion.
