Pilomyxoid astrocytoma of the cerebellum.

Pilomyxoid astrocytomas (PMAs) are low-grade (WHO Grade II) tumors for which the imaging features are similar to pilocytic astrocytomas (PAs), but for which histological features and the clinical course differ. They are classified as a variant of PA. They have only been recently recognized, and they behave more aggressively than PAs. Most cases occur in the hypothalamic-chiasmatic area, although they may be located in any part of the neuraxis. Posterior fossa PMAs are very rare. The authors report a case of a 2-year-old girl with cerebellar PMA.