Mediastinal gastroenteric cyst in a neonate containing respiratory-type epithelium and pancreatic tissue.

Mediastinal gastroenteric cyst is an uncommon congenital malformation and a distinct histopathological entity within the family of foregut duplication cysts. This lesion is mainly encountered in neonates and infants. Histologically, it is characterized by double-layered smooth muscle wall and gastric lining mucosa. We report on a case of a 2-day-old girl, with a posterior mediastinal cystic mass associated with T3-T4 hemivertebrae, presenting with severe respiratory distress. The cyst was multilocular, surgically removed, and histopathologic analysis revealed that it was of gastroenteric type. However, in numerous areas of the lesion, respiratory-type epithelium was observed, as well as pancreatic tissue. After removal of the lesion the patient made an uneventful recovery and shows no signs of long-term pulmonary sequelae. We failed to demonstrate in the available literature the presence of this variable epithelial lining within a single mediastinal foregut cyst. In addition, pancreatic tissue within an intrathoracic enteric cyst has been reported only twice.