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|Classification and external resources|
|Classification and external resources|
Pilocytic astrocytoma or juvenile pilocytic astrocytoma or cystic cerebellar astrocytoma (and its variant juvenile pilomyxoid astrocytoma) is a neoplasm of the brain that occurs more often in children and young adults (in the first 20 years of life). They usually arise in the cerebellum, near the brainstem, hypothalamic region, or the optic chiasm, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. These tumors are usually slow growing. The neoplasms are associated with the formation of a single (or multiple) cyst(s), and can become very large.
The pilocytic astrocytoma is, in general, considered a benign tumor. It is often cystic, and, if solid, it tends to be well-circumscribed. It is characteristically a contrast-enhancing tumor by current imaging investigations (e.g., CT scan, MRI)
Children affected by pilocytic astrocytoma can present with different symptoms that might include failure to thrive (lack of appropriate weight gain), headache, nausea, vomiting, irritability, torticollis (tilt neck or wry neck) difficulty to coordinate movements and visual complaints (including nystagmus). The complaints may vary depending on the location and size of the neoplasm. The most common symptoms are associated with increased intracranial pressure due to the size of the neoplasm.
According to a Dutch source juvenile pilocytic astrocytoma occurs at a rate of 2 in 100,000 people. Most affected are children ages 5–14 years.
Tumors of the optic pathway account for 3.6-6% of pediatric brain tumors, 60% of which are juvenile pilocytic astrocytomas. Astrocytomas account for 50% of pediatric primary central nervous system tumors. About 80-85% of cerebellar astrocytomas are juvenile pilocytic astrocytomas. Quoted from emedicine 
Recent genetic studies of pilocytic astrocytomas show that some sporadic cases have gain in chromosome 7q34 involving the BRAF locus (Bar et al., 2008).
Usually—depending on the interview of the patient and after a clinical exam which includes a neurological exam, and an ophthalmological exam—a CT scan and or MRI scan will be performed. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify. The neoplasm will be clearly visible.
If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy of it. This simply involves the removal of a small amount of tumorous tissue, which is then sent to a (neuro)pathologist for examination and staging. The biopsy may take place before surgical removal of the tumor or the sample may be taken during surgery.
Macroscopically, an astrocytoma is a mass that looks well-circumscribed and has a large cyst. The neoplasm may also be solid.
Under the microscope, the tumor is seen to be composed of bipolar cells with long "hairlike" GFAP-positive processes, giving the designation "pilocytic" (that is, made up of cells that look like fibers when viewed under a microscope). Some pilocytic astrocytomas may be more fibrillary and dense in composition. There is often presence of Rosenthal fibers, eosinophilic granular bodies and microcysts. Myxoid foci and oligodendroglioma-like cells may also be present, though non-specific. Long-standing lesions may show hemosiderin-laden macrophages and calcifications.
Surgery is often the treatment of choice. Total resection is often possible; however, the location could prohibit access to the neoplasm and lead to incomplete or no resection at all. Removal of the tumor will generally allow functional survival for many years. . In particular for pilocytic astrocytomas (that are commonly indolent bodies that may permit normal neurologic function) surgeons may decide to monitor the neoplasm's evolution and postpone surgical intervention for some time. However, left unattended these tumors may eventually undergo neoplastic transformation.
Some articles mention ultrasonic aspiration as a minimal invasive technique for solid neoplasms.
Because of the age of people diagnosed with pilocytic astrocytoma, the treating medical team will often try to avoid radiotherapy and chemotherapy in order avoid damage to the developing brain. There is evidence in literature to suggest that the careful use of chemotherapy and/or radiation therapy may be useful as a complementary treatment in case of incompletely resection of the neoplasm.
Children with cerebellar pilocytic astrocytoma may experience side effects related to the tumor itself and related to the treatment. Strabismus.
Any person undergoing brain surgery may suffer from epileptic seizures.
Parents of children after surgery should be made aware of this fact and should be prepared to take adequate action in case of the seizure (see brain tumor)
Common side effects of chemotherapy includes nausea, vomiting and decreased blood counts (i.e. anemia).
Juvenile pilocytic astrocytomas that are initially characterized according to WHO grade I have been found to undergo malignant transformation following radiation treatment.
Radiation therapy may cause swelling related to tissue inflammation.
The recommended course of action according to different literature sources is to monitor and reattempt a complete surgical removal. In cases of progressive/recurrent disease or when maximal surgical removal has been achieved, chemotherapy and/or radiation therapy will be considered by the medical team.