Pilomyxoid astrocytoma

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Status

Done

General

A variant of pilocytic astrocytoma

Definition

Essential

A monomorphic, loose, myxoid neoplasm with piloid cytology and prominent angiocentnc pattern, often without Rosenthal fibres and eosinophilic granular bodies OR
An astrocytic neoplasm with pilomyxoid features and a solitary МАРК alteration, such as KIAA1549.BRAFfusion

Numbers

Age

Tumour of infancy

CNS WHO grading

Grade 2

Localisation

Hypothalamic/chiasmatic (most common)

Less common:

Thalamus
Cerebellum
Brain stem
Temporal lobe
Spinal cord

Genetic

Similar to Pilocytic astrocytoma

Clinical features

Depends on anatomical site

Radiological

Pilomyxoid astrocytomas appear similar to classic pilocytic astrocytomas, but they are more often solid and uniformly enhancing

Fig. 2.11 Pilomyxoid astrocytomas are usually large, contrast-enhancing masses that are most frequent in the hypothalamic and suprasellar areas. — Pilomyxoid astrocytomas are usually large, contrast-enhancing masses that are most frequent in the hypothalamic and suprasellar areas.

A close-up of a brain scan AI-generated content may be incorrect. — Pilomyxoid astrocytoma. Tumour in a 7-month-old girl. There was spinal and brainstem dissemination at diagnosis. She had three recurrences over the following 4 years while being treated with trametinib with partial response. The tumour has BRAF kinase domain duplication with KIAA1549::BRAF gene fusion. Contrast-enhanced MRI: A Coronal. B Axial. C Sagittal.

Histopathology

Perivascular orientation of tumour cells is a distinctive feature of pilomyxoid astrocytoma.

Fig. 2.12 Perivascular orientation of tumour cells is a distinctive feature of pilomyxoid astrocytoma.

Prognosis

Poorer outcome than classic pilocytic astrocytoma

Higher rate of recurrence

Some pilomyxoid astrocytomas develop into a classic pilocytic astrocytoma on recurrence

A propensity for CSF dissemination

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