MR imaging of fetal sacrococcygeal teratoma: diagnosis and assessment.
OBJECTIVE: The purpose of this study was to evaluate the usefulness of MR imaging in the diagnosis and assessment of fetal sacrococcygeal teratoma and to determine if MR imaging provides information not seen on obstetric sonography. SUBJECTS AND METHODS: Twelve pregnant women were referred for fetal MR imaging of sacrococcygeal teratoma seen at obstetric sonography. The presence, size, content extension, and compressive effects of each mass were determined and correlated with the sonographic findings and with postnatal studies, including surgery and pathology. The extent of each sacrococcygeal teratoma was classified according to the American Association of the Pediatrics Surgery Section (types I-IV). RESULTS: There is a complete agreement of sonographic and MR imaging measurements. The sacrococcygeal teratomas appeared cystic with few septa in three fetuses, markedly septated or even microcystic in eight, and completely solid in one. The sonographic description of the content corresponded well to MR imaging findings in 10 of 12 fetuses. An agreement on the extent of each mass was observed in nine patients, whereas there is a disagreement in three, including in one fetus with an extension of the tumor within the spinal canal recognized only at MR imaging. The MR imaging findings were confirmed by postnatal studies in 10 patients. CONCLUSION: Sacrococcygeal teratomas had characteristic MR imaging appearances that allowed a complete assessment in most fetuses. Because of MR imaging, the prenatal evaluation was changed in some patients and affected counseling of the parents and treatment. MR imaging is a valuable adjunct to obstetric sonography for the prenatal evaluation of sacrococcygeal teratoma.