Case of the month: January 1999--Fetus with echogenic mass in third ventricle.

A 29-week gestational age newborn male infant was found to have an echogenic mass in the 3rd ventricle by prenatal ultrasound 2 weeks prior to delivery. At delivery he was poorly responsive and had hydrocephalus and ascites. A CT scan after birth showed cerebral infarction, amorphous tissue in the left hemisphere and numerous calcifications. Despite supportive treatment he died 4 days after birth. Postmortem examination of the brain revealed marked distortion of the architecture and a supratentorial undifferentiated neoplasm consistent with a PNET. The tumor showed extensive areas of hemorrhage and necrosis and involvement of lateral and third ventricles, brain parenchyma, and meninges.