title: Fetus-in-fetu presenting as cystic meconium peritonitis: diagnosis, pathology, and surgical management.
abstract: Fetus-in-fetu (FIF), a rare congenital anomaly, is a fetus incorporating the well-differentiated tissue of its twin. The authors describe a newborn who presented with massive abdominal distension and severe respiratory distress. Abdominal x-rays showed multiple calcifications. The diagnosis of meconium pseudocyst was made. At emergency laparotomy an irregular fetiform mass was found in the retroperitoneum lying within a fluid-filled amniotic sac. It contained a vertebral column, 10 limblike structures, and cranial and caudal ends, supporting the diagnosis of fetus-in-fetu. This case highlights several important points. FIF often is overlooked in the differential diagnosis of a newborn abdominal mass and, as in this case, may be confused with meconuim pseudocyst. FIF should be differentiated from a teratoma because of the latter's malignant potential. Because this diagnosis is not made until pathological analysis, all parts of the mass should be removed to prevent malignant recurrence.
authors.affiliation: Department of Laboratory Medicine and Pathology, Stollery Children's Health Centre, University of Alberta, Edmonton, Canada.
authors.forename: R G
authors.initials: RG
authors.lastname: Khadaroo
authors.forename: M G
authors.initials: MG
authors.lastname: Evans
authors.forename: L H
authors.initials: LH
authors.lastname: Honore
authors.forename: R
authors.initials: R
authors.lastname: Bhargava
authors.forename: E
authors.initials: E
authors.lastname: Phillipos
mesh_terms: D000005:Abdomen / Q000473:pathology / Q000601:surgery; D000328:Adult; D002114:Calcinosis / Q000175:diagnosis* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D005333:Fetus / Q000002:abnormalities* / Q000473:pathology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D007231:Infant, Newborn; D007813:Laparotomy; D008470:Meconium; D008639:Mesenteric Cyst / Q000175:diagnosis* / Q000601:surgery; D010538:Peritonitis / Q000175:diagnosis* / Q000473:pathology; D011247:Pregnancy; D011860:Radiography, Abdominal; D013724:Teratoma / Q000175:diagnosis; D016896:Treatment Outcome; D014430:Twins, Monozygotic