Prenatal Imaging of Fetal Sacrococcygeal Teratoma: Complementary Roles of Ultrasound and Magnetic Resonance Imaging

Abstract

Purpose: Congenital Sacrococcygeal Teratoma (SCT) is the most common solid tumor of the fetus, with a birth prevalence of approximately 1 in 20,000 to 1 in 40,000 live births. The increase in the number of cases of prenatally diagnosed SCT due to the widespread use of anomaly ultrasound scanning makes it vital to conduct proper prenatal evaluation of fetuses. This paper aims to review the role of ultrasound and fetal MRI as diagnostic methods for evaluating prenatally SCTs.

Methods: A narrative literature review was performed by searching PubMed/MEDLINE and EMBASE for peer-reviewed, English-language studies published between 1990 and 2025.

Conclusion: Prenatal ultrasonography examination is widely applied as the main imaging method for the prenatal diagnosis of SCTs. Features with a bad prognosis on ultrasound scans are predominance of solid SCT morphology, highly vascular tumor, fast growth of the tumor, placentomegaly, and fetal hydrops. MRI provides more detailed evaluation of intrapelvic tumor infiltration, soft tissue composition, and involvement of the spinal canal in SCTs in particular in Altman types II-IV. Prognostic markers of the imaging include tumor volume-to-fetal weight ratio, tumor growth rate, and solid tumor proportion. Ultrasound remains the first-line modality for detection, hemodynamic assessment, and surveillance, whereas MRI is a complementary second-line modality for defining intrapelvic and spinal extent, particularly in Altman types II-IV or when ultrasound is inconclusive.