Case Report: Imaging features of fetal intracranial immature teratoma.

Fetal intracranial immature teratomas are exceedingly rare. In most cases, the exact site of origin cannot be determined. Early and accurate diagnosis plays a pivotal role in pregnancy management and delivery planning, making imaging evaluation particularly important. However, prenatal imaging diagnosis remains challenging. We report a case of fetal immature teratoma confirmed by autopsy pathology, with comprehensive prenatal and post-induction imaging examinations. Prenatal ultrasound revealed a mixed echogenic mass at the base of the fetal skull with multiple hyperechoic foci, and CDFI demonstrated relatively abundant internal vascular signals. Prenatal MRI demonstrated a mass-like intracranial lesion with heterogeneous signal intensity, closely related anteriorly to the middle cranial fossa. The adjacent brain parenchyma was compressed and displaced, with indistinct cerebral sulci and gyri and thinning of the cerebral cortex. Post-induction MRI showed partial protrusion of the intracranial lesion into the left lateral ventricle, without evident fat signal. Post-induction CT further demonstrated multiple calcifications within the portion of the lesion extending into the left lateral ventricle. Prenatal ultrasound can detect calcifications and vascularity within fetal intracranial immature teratomas, whereas prenatal MRI offers superior lesion localization, overall visualization, delineation of relationships with adjacent brain structures, and evaluation of invasion extent. The complementary use of both modalities provides significant advantages in improving diagnostic accuracy.