Pilomyxoid astrocytoma of the fornix imitating a colloid cyst

Pilomyxoid astrocytoma is a recently described pediatric brain tumour with distinct histological features and has been shown to behave more aggressively than pilocytic astrocytoma. Pilomyxoid astrocytomas usually involve the hypothalamic/chiasmatic region with imaging features similar to pilocytic astrocytoma. We report a case of pilomyxoid astrocytoma in the fornix with imaging features imitative of colloid cyst.