Mesothelial inclusion cysts represent benign lesions that have been reported in a wide variety of locations. Peritoneal cysts are observed and visceral involvement has been described, notably of intraperitoneal organs such as the spleen and the testis. We report the cases of 2 neonates who underwent surgical management of an omphalocele. The hernial sac contained an accessory liver lobe, displaying in both cases multilocular mesothelial inclusion cysts. The hobnail cells lining the cysts exhibited calretinin and cytokeratin immunohistochemical reactivity, as well as focal D2–40 reactivity. One of the cases occurred in the setting of a Beckwith-Wiedemann syndrome (MIM 130650), an overgrowth disorder notably associated with omphalocele and hepatic anomalies and tumors. However, no hepatic mesothelial cyst has been described in this syndrome. In the 2nd case the omphalocele and the hepatic cysts were the sole lesions observed in the neonate. To the best of our knowledge, these 2 cases represent the first description of such an association.

Keywords: accessory liver lobe, congenital cyst, mesothelial cyst, omphalocele