Pilocytic astrocytoma
- Grossly tumor is well demarcated. cystic degeneration is seen.
Microscopic examination
- Biphasic appearance with alternating dense and loose/microcystic component
- Dense regions resemble fibrillary astrocytoma except that cytoplasmic processes are particularly long and hair like (piloid)
- Presence of Rosenthal fibres which are brightly eosinophilic cork screw shaped is characteristic
- Cells have round to oval nuclei with bland chromatin.
- Other features are
- Mulberry shaped eosinophilic granular bodies
- Multinucleated forms
- Glomeruloid vessels with multiple lumina
- Oligodendroglial like cells
- Infarct like necrosis in 5% to 10% of cases
- Pilomyxoid astrocytoma is characterized by mucoid stroma, monomorphous bipolar cells and angiocentric arrangement of cells. No Rosenthal fibres or eosinophilic granular bodies