WHO Grade 1 astrocytoma (non-infiltrative or Localised).
Children and young adults.
Discrete borders. Well circumscribed. Benign. Cystic with Mural nodule +.
Site: Third ventricle, optic nerve, spinal core and cerebrum.
MAP kinase pathway alterations. Eg: KIAA1549-BRAF fusion.
No IDH mutation in WHO grade I astrocytoma (only for grade II and III).
Microscopy
- Bipolar cells with hair like process
- Fibrillary / Microcystic stroma
- Rosenthal fibres – Eosinophilic corkscrew structures.
- Mulbery-like inclusions – Eosinophilic granular bodies.