Abstract
Mature cystic teratomas (MCTs) arise from totipotent cells. While the ovaries are the most common sites, extragonadal teratomas are very rare. This case report describes the clinical details of a 20-year-old woman who was found to have a large pelvi-abdominal mass on clinical and imaging studies and elevated levels of CA-125. Because of the uncertainties of the origin of the mass, a multidisciplinary team suggested exploratory laparotomy with a mesenteric cyst as a differential diagnosis. Laparotomy showed both ovaries to be normal and revealed a large omental MCT, which was excised. Histopathology confirmed the diagnosis.