Pilomyxoid Astrocytoma Presenting as Fetal Ventriculomegaly and Obstructive Hydrocephalus in a Newborn: A Case Report

Pilomyxoid astrocytoma (PMA) is a histologically distinct and biologically aggressive variant of pilocytic astrocytoma (PA), with neonatal-onset presentation being extremely rare.We report a term neonate who presented with refractory seizures and progressive macrocephaly, in whom antenatal ventriculomegaly had been detected at 26 weeks of gestation.Postnatal neuroimaging revealed a large suprasellar mass causing obstructive hydrocephalus, for which an emergency ventriculoperitoneal shunt was performed, followed by subtotal surgical resection.Histopathology showed monomorphic bipolar cells in an angiocentric pattern within a myxoid matrix, with diffuse S-100 positivity and focal perivascular GFAP immunoreactivity, confirming PMA.The postoperative NICU course was prolonged with multisystemic complications, and the infant was discharged on day of life 77.This case highlights that antenatal ventriculomegaly, even when mild, may herald an underlying congenital intracranial neoplasm, supporting consideration of postnatal neuroimaging follow-up.PMA should be considered in the differential diagnosis of a neonate presenting with a suprasellar mass or unexplained obstructive hydrocephalus, and requires histopathological confirmation given significant radiological overlap with classic pilocytic astrocytoma.