As defined by the Fleishchner Society glossary of terms, lung cysts are round parenchymal lucencies or low-attenuation areas with well-defined interfaces with normal adjacent lungs. They are characteristically thin-walled structures with walls less than 3 mm in size, usually containing air, but also fluid or solid material.
Isolated pulmonary parenchymal cysts are seen commonly on computed tomography, but we should be aware that there is also a wide heterogeneous group of diseases associated with lung cysts, making the differential diagnosis challenging. Thus, for radiologic assessment of cystic lung diseases, it is very important to differentiate true lung cysts from other air-space lesions (cyst-like lesions), in order to achieve an accurate diagnosis.