Yolk sac tumor of the fourth ventricle in a 3-year-old boy: imaging features.

Yolk sac tumor (YST) is a rare malignant germ cell tumor and typically occurs in gonads. It is extremely rare in the brain, especially in the fourth ventricle.This study reported the case of a 3-year-old boy with intermittent vomiting for 11 days and then intermittent twitch for 5 h.Brain computed tomography showed a slightly higher density mass in the fourth ventricle. Brain magnetic resonance imaging showed an irregular lobulated expansive mass in the fourth ventricle, appearing with the low intensity on T1-weighted images, and uneven hyperintensity on T2-weighted images. The enhanced scan showed inhomogeneous and strong enhancement, with multiple small cyst-like areas of no enhancement. Tortuous tumor vessel also can be seen. The pathological results after surgical resection showed an YST in the fourth ventricle.When a mass is observed in the fourth ventricle in children, with uneven signal with hemorrhage and cystic change, inhomogeneous and strong enhancement, and facilitated diffusion on diffusion-weighted imaging, YST should be considered. The increase of α-fetoprotein value can help differential diagnosis.