Tip-136;Supratentorial Midline Pilocytic Astrocytoma

Tip-136; Pilocytic astrocytoma is an astrocytic neoplasm with variable proportions of bipolar hair-like, pilocytic, cells, compact and loose or myxoid regions, Rosenthal fibers, and eosinophilic granular bodies. It accounts for 5% of all CNS tumors and is typically encountered in the first 2-decades of life, representing the most common glioma in childhood. Pilocytic astrocytoma is associated with MAPK pathway gene alterations, most often KIAA1549::BRAF gene fusions, and it is considered the prototype for circumscribed astrocytoma. It is CNS WHO grade 1.  Some tumors may mimic diffuse astrocytoma on histopathology because of a surprising degree of infiltration, which is further highlighted by NFP immunostain, despite often appearing solid radiologically.