Low attenuation - Cystic diseases

Pulmonary cysts present as circumscribed and radiolucent lesions with a thin wall (usually <3 mm thick). They are often caused by fibrotic changes resulting in honeycombing. These cysts can have a diameter ranging from several millimetres to several centimetres. Adjacent cysts share the wall, a finding not seen in other cystic lung diseases.2 

Cystic lung diseases include lymphangioleiomyomatosis, Langerhans cell histiocytosis, lymphocytic interstitial pneumonia, pneumatoceles.9

Low attenuation - Cystic diseases