The role of computed tomography in a diagnostic approach to cystic lung diseases and their differential diagnosis

Abstract

In everyday routine, lung cysts are commonly seen in Computed Tomography, as far as many different conditions and diseases are associated with air cysts. Thus, correct diagnosis of cystic lung diseases, which show a wide spectrum, is a challenge for radiologists. For diagnosis and differential diagnosis, fifi rst of all, cysts should be distinguished from such other air fifi lled lesions, like cavities, bullae, pneumatocele, emphysema, honeycombing and cystic bronchiectasis. Second, cysts can be categorized as single/localized versus multiple/diffuse. Solitary/localized cysts include incidental cysts, congenital cystic diseases and cystic cancers. Multiple/diffuse cysts can be further categorized according to the presence or absence of associated radiologic fifi ndings. Multiple/diffuse cysts without associated fifi ndings include lymphangioleiomyomatosis and Birt-Hogg-Dubé syndrome. Multiple/diffuse cysts may be associated with ground-glass opacity or small nodules. Multiple/diffuse cysts with nodules include Langerhans cell histiocytosis, cystic metastasis and amyloidosis. Multiple/diffuse cysts with ground-glass opacity include pneumocystis pneumonia, desquamative interstitial pneumonia and lymphocytic interstitial pneumonia. The stepwise radiologic diagnostic approach can be helpful in reaching a correct diagnosis for various cystic lung diseases.