Bronchogenic Cyst

Pathophysiology:  part of the spectrum of 'bronchopulmonary foregut' malformations that result from abnormal embryogenesis of the fetal foregut.  The spectrum includes (1) bronchogenic cysts  (2) esophageal duplication cysts  (3) bronchial aplasia/dysplasia  (4) pulmonary aplasia/dysplasia and (5) tracheo-bronchial fistulas

CXR Findings:

1. very thin walled cyst usually several centimetres in diameter, most commonly seen in the middle or posterior mediastinum in the mid retro or infracarinal area
2. second most common site is in the periphery of the lower lungs

Clinical/Radiological Clues: 

Complications frequently occur, usually infection, with an air-pus fluid/blood level in the cyst.  Infected bronchogenic cysts usually respond to antibiotic treatment, though rarely, a regional lung resection is done.

"Aunt Sophies":

1. small bulla or bleb
2. area of bullous emphysema
3. pneumatocele
4. old tuberculosis or fungal infection with thin walled cavities, or areas of air trapping