Pulmonary cysts

Thin-walled (≤2 mm), air-filled parenchymal lucencies on CT with a well-defined interface with adjacent normal lung, distinct from cavities, emphysema, and bronchiectasis, and may be isolated or part of diffuse cystic lung disease. Possible causes are smoking, Pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dubé syndrome, tuberous sclerosis, lymphangioleiomyomatosis, pneumonia, and lung abscess.