**5.1. Definition and incidence**

It comes from the primitive foregut early in the embryogenesis. It contains the columnar ciliary epithelium and the cartridges. They are usually located intrapulmonary but may also be mediastinal [25], or intrapericardial. They may also be located cervical or infradiaphragmatic. They can basically be located anywhere on the tracheoesophageal tract. It is extremely rare.
