Fetal Interhemispheric Lipoma: An Incidental Finding on Third-Trimester Ultrasound

Abstract

Introduction: Cerebral lipomas are among the rarest congenital malformations of the central nervous system. They correspond to mesenchymal-type tumors composed of mature adipocytes, most of which are benign and slow-growing. When they develop within the central nervous system, they may be associated with other anomalies, one of which is dysgenesis or agenesis of the corpus callosum. Methodology: We present the case of a 31-year-old patient at 31+6 weeks of pregnancy. During an ultrasound performed to assess fetal growth, an elongated hyperechogenic image suggestive of an interhemispheric lipoma was detected in the anterior brain at the interhemispheric region. Results: Following this finding, the patient was referred to her corresponding referral hospital for a fetal magnetic resonance imaging (MRI) study in order to better characterize the lesion. The MRI confirmed a corpus callosum lipoma associated with hypogenesis of the corpus callosum. The medical team, together with the treating physician, decided to opt for expectant management until the end of the pregnancy. Conclusion: The presented case not only contributes to the international literature on this topic, but also highlights the importance of recognizing uncommon congenital malformations that may occur in the fetus during pregnancy, as well as the current lack of clear information regarding their prognosis, which complicates counseling for the parents involved.