Mesenteric hibernoma in a pediatric patient present on prenatal ultrasound

A 15-month old male presented with several months of abdominal distension. After undergoing thorough workup, he was found to have an intraabdominal mass on imaging. He underwent exploratory laparotomy and resection of a mesenteric mass along with a loop of associated small bowel. On pathology, the mass was consistent with a hibernoma. In retrospect, the mass may have been present on prenatal ultrasound.Hibernomas are rare, adipocytic tumors of brown fat origin. There have been less than 20 cases of pediatric hibernomas reported in the English literature. Moreover, there have been no previous reports of mesenteric hibernomas in children or those recognized on prenatal imaging. While lipomatous abdominal tumors are exceedingly rare in the neonatal population, this case report highlights that unusual volume of intra-abdominal fat seen on prenatal ultrasound may warrant repeat evaluation in the perinatal period.