Large mesenteric lipoma ultrasonographically mimicking a mature cystic teratoma during pregnancy

Primary tumors arising between the leaves of the mesentery are rare in comparison with malignant implants from intra-abdominal or pelvic tumors or metastases to mesenteric lymph nodes, which occur more commonly. We present an unusual case in which a large solid mass at 19 weeks' gestation, considered consistent with a mature cystic teratoma of the ovary, proved at exploratory laparotomy to be a mesenteric lipoma, and we discuss the sonographic and computed tomographic findings of this lesion.