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...