Esophageal and enteric duplication cysts are foregut-derived developmental anomalies most commonly encountered in the mediastinum and rarely in the abdomen.^{1,2,3,4,5,6,7,8} The duplication of the hollow structures of the digestive tract manifests three essential points: (1) attachment to at least one point of the alimentary tract, (2) epithelium resembling some part of the alimentary tract, and (3) welldeveloped coat of smooth muscle (double-layered smooth muscle wall).^7,9,10

Intramural esophageal cysts result from defects in the tubulation process and are not associated with vertebral anomalies.⁷ In contrast, enteric cysts are usually separate from the esophagus and lie in the posterior mediastinum. They are commonly associated with vertebral anomalies and are part of split notochord syndrome.^1,9

Among alimentary tract duplication cysts, 20% occur in the mediastinum.⁹ The majority of duplications are found in children, the frequency being almost triple to that found in adults.⁹ The commonest mode of presentation in the neonatal period is respiratory distress. In adults, they can be discovered as an incidental finding on chest radiograph. About two-thirds of alimentary tract cysts are right sided.⁷

Intramural esophageal and enteric cysts are unilocular. The lesions are thin walled and translucent, with a tan, smooth, and glistening outer surface. The inner lining of the cyst is smooth, without papillary projections. The cysts contain pink serous or yellow-gray mucinous fluid.

Intramural esophageal cysts contain at least two types of epithelium, including ciliated or nonciliated columnar, squamous, or a mixture of these types, heterotopic lung tissue, thyroid stroma, ganglia, and two smooth muscle layers.^6,7,10,11,12 Heterotopic gastric mucosa and well-differentiated lymphoid aggregates resembling Peyer patches are rarely observed.