Pilocytic astrocytoma is a neoplasm of the brain arising from astrocytes in children. It is a low-grade tumor (I/IV). The most common location is below the tentorium i.e., cerebellum. It is less commonly found on the floor of the third ventricle or cerebral hemisphere.
Two types of alteration in the BRAF gene are implicated in pilocytic astrocytoma:
1. Translocation of a gene separates the kinase domain and the inhibitory domain.
2. Activating mutations of V600E genes
Pilocytic astrocytoma may also occur due to loss of function of the neurofibromin gene associated with neurofibromatosis type I.
Morphologically, pilocytic astrocytoma range from cystic appearance to solid, well-circumscribed mass. The hair-like processes are the characteristic finding demonstrated on histopathology. These fibers are called Rosenthal fibers. They form fibrillary meshwork which is GFAP-positive.
Tumors are usually treated by surgical resection. It has a good prognosis.
Robins and Cotran Pathological Basis of Disease
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