Sections show a 2mm piece of mildly hypercellular tumour composed of mildly enlarged, oval, hyperchromatic nuclei with small nucleoli. There are scattered Rosenthal fibres and eosinophilic granular bodies present. A single mitosis is identified. No necrosis or microvascular proliferation is seen.
Immunohistochemical results show tumour cells stain:
- GFAP: Positive
- Nestin: Positive
- NogoA: Negative
- IDHl R132H: Negative
- ATRX: Positive
- p53: Positive
- p16: Positive
- Co99: Positive
- EMA: Negative
- BRAFV60oE: Negative
- Topoisomerase proliferation index: 1%
- BRAF mutation c.1799T>A (V60oE) NOT DETECTED
- BRAF-KIAA1549 translocation NOT DETECTED
- H3F3A (H3.3A) MUTATION STATUS Codons 27 and 34 of the H3F3A gene are sequenced by pyrosequencing.
DIAGNOSIS: pilocytic astrocytoma (WHO Grade I).