Figure 14b. Intracranial teratoma. (a) Transverse US image of a fetal brain shows a large, heterogeneous mass within the cranial vault (cursors) completely destroying normal anatomic landmarks. Measurements showed marked macrocephaly. (b) Postmortem coronal T1-weighted image demonstrates complete replacement of brain tissue by a complex mixed-signal-intensity mass. Immature teratoma (with primitive neural tissue, cartilage, bone, intestinal mucosa, smooth muscle, and hemorrhage) was identified at autopsy.