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Pilomyxoid astrocytoma

Case contributed by Dr Kapilan Varatharajah


Positional headache and blurred vision.

Patient Data

Age: 20
Gender: Female

ASNR 2016: This case was submitted as part of the American Society of Neuroradiology (ASNR 2016) Case Of The Day competition, in collaboration with 


There is a large predominantly cystic mass arising from the inferior left cerebellar hemisphere. A solid enhancing component isdemonstrated inferiorly. There is considerable associated mass effect with partial compression of the inferior fourth ventricle. The lateral and third ventricles are dilated. There is deformity of the left cerebellar peduncle and distortion of the adjacent brainstem.


Centered in the medial aspect of the left cerebellar hemisphere, there is a mixed solid and cystic mass. The solid component is located medially and enhances vividly and homogeneously. There is a cystic component superiorly within the cerebellum, as well as inferiorly, extending as far as the upper cervical spinal cord. The cystic component is located posterior to the cord here, and there is mild flattening of the cord.

There is peripheral enhancement of the cystic component of the mass. The solid component demonstrates homogeneous T2 hyperintensity. There are no flow void is identified.

There is mild surrounding vasogenic edema. The mass compresses the fourth ventricle, and there is obstructive hydrocephalus with evidence of mild transependymal CSF flow.

The patient proceeded to craniotomy and resection. 


MICROSCOPIC DESCRIPTION: Paraffin sections show a moderately hypercellular glial tumor involving cerebellum. Tumor cells are a mixture of plump piloid cells and cells with round and oval nuclei and delicate processes. Both cell types show moderate nuclear pleomorphism. No mitotic figures are identified. There is no microvascular proliferation and no necrosis is seen. Small numbers of Rosenthal fibers are identified. A moderate amount of extracellular Alcian Blue positive myxomatous material is noted throughout the tumor. Tumor gradually merges with surrounding cerebellar parenchyma. Gliosis and patchy loss of Purkinje cells is noted in the cerebellar cortex.

IMMUNOHISTOCHEMISTRY: GFAP positive Nestin positive (moderate) ATRX positive (not mutated) IDH-1 R132H negative (not mutated) MGMT positive (likely unmethylated) p53 negative p16 negative Topoisomerase labeling index: Approximately 2%. The features are of pilomyxoid astrocytoma (WHO Grade II).

DIAGNOSIS: Pilomyxoid astrocytoma (WHO Grade II)

Case Discussion

Pilomyxoid astrocytomas is a low-grade glial series tumor, which is a rare variant of the more common pilocytic astrocytoma. 

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