Mediastinal esophageal duplication cyst associated with a partial pericardial defect.

A two-year-old girl with a mediastinal esophageal duplication cyst is the twelfth example of a thoracic cyst of foregut origin or pulmonary "sequestration" (bronchopulmonary foregut malformation according to the expanded definition of Gerle et al.) that has been associated with a partial pericardial defect on the same side, suggesting that anomalous thoracic masses of several morphologic types have a similar pathogenesis.