The patient went on to have a craniotomy and resection of the mass.
Histology
MICROSCOPIC DESCRIPTION:
Sections of the cerebellum show a moderately cellular glial tumour. The tumour forms fasciculi of bipolar cells as well as focal microcystic change, containing mucoid material. Other cells form small aggregates, with a spongioblastoma polare-like pattern. Generally, the tumour cells have mildly enlarged and hyperchromatic nuclei. Some cells have perinuclear haloes (oligodendroglial-like cells). Multinucleated forms are seen. Many Rosenthal fibres and eosinophilic granular bodies are intermixed with the tumour cells. Scattered clumps of basophilic calcification are identified. No mitoses are seen. Some of the blood vessels are hyalinised and small numbers of perivascular lymphocytes are present. There is no endothelial cell hyperplasia or necrosis. The features are those of pilocytic astrocytoma. The Ki-67 index is 1%.
DIAGNOSIS:
Pilocytic astrocytoma (WHO Grade I).
The patient was routinely followed up.