For many years the only mechanism for observing gross pathologic features of CNS neoplasms was to examine brains extracted after death. However, advancements in imaging technology now allow providers to observe typical gross neuropathological findings in the brains of living patients. Some brain tumors have characteristic MRI findings, an example of which is a cyst... Continue Reading →
Pilocytic Astrocytoma (PA) characteristically exhibits biphasic morphology featuring densely fibrillar, compact regions alternating with loosely-cohesive microcystic or myxoid areas; the latter is pictured here. Diagnosis can be difficult, especially on small biopsies, but molecular testing can help. BRAF-KIAA1549 fusion occurs in about 70% of PAs, whereas BRAF V600E mutation occurs in about 5-10% of PAs.
Pilocytic astrocytoma is a circumscribed glioma (WHO Grade I) commonly found in children and young adults. Characteristic features include piloid cells with long, thin, hair-like cytoplasmic processes and a myxoid background, which are both seen here in this medium power image of a cytologic smear preparation performed during intraoperative consultation.
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Stemming from the Latin word "Pilos", meaning "resembling or composed of hair", pilocytic astrocytomas are named as such because of their long hair-like gliofibrillary processes (clear arrows) that stem off of slender bipolar nuclei (black arrows), which are best seen on smear preparation of fresh tissue (depicted here).