Pilocytic astrocytoma - craniocervical junction
Lower limb weakness.
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A large mixed multicystic and solid mass is seen centred at the cervico medullary junction. Cystic components are seen within the posterior fossa, at least one of which has blood products layering within it and adjacent haemosiderin staining. A cystic component extends into the fourth ventricle and abuts the left middle cerebellar peduncle. There are solid enhancing components of the mass in the upper cervical cord. The cord is only imaged to the mid cervical level, at which point the cord remains expanded. Elements of the lesion have elevated cerebral blood volume (CBV). There is marked crowding at the foramen magnum.
The mixed solid and multicystic mass centred at the cervical medullary junction extends inferiorly to at least the C4-C5 level, where there are cystic components, but only faint enhancement. The craniocaudal diameter of the lesion is at least 10 cm. Between the C5 and T2/3 levels, the cord is diffusely expanded with high T2 signal involving most of the cross sectional area. Inferior to the T2/3 level, the thoracic spinal cord is of normal volume and signal intensity with no abnormal enhancement identified.
There is evidence of obstructive hydrocephalus with distension of the lateral and third ventricles and effacement of the cortical sulci of the cerebral hemispheres.
Findings compatible with tumour centred at the cervico medullary junction, differential diagnosis is between a pilocytic astrocytoma and spinal cord ependymoma.
The patient went on to have a posterior fossa craniotomy and debulking of the tumour.
Paraffin sections show fragments of a moderately hypercellular astrocytic glioma. Tumour cells are a mixture of piloid cells with elongated spindle shaped hyperchromatic nuclei with bipolar processes and cells with round and oval nuclei which are sometimes arranged in fluorettes. The piloid cells are arranged in loose fasciculi. There are prominent Rosenthal fibres. No mitotic figures are identified. There is no microvascular proliferation or necrosis.
- GFAP positive
- IDH-1 R132H negative
- p53 negative
- p16 negative
- Topoisomerase labelling index: Approximately 1%
Pilocytic astrocytoma (WHO Grade I)