Pulmonary cysts are frequently encountered at thoracic computed tomography, often incidentally detected. For patients older than 40 years of age, a few pulmonary cysts found at thoracic computed tomography can be a normal finding. The etiologies of pulmonary cysts are numerous, and cysts should be distinguished from other focal lucent lung lesions, such as the numerous causes of cavitary lung disease, bronchiectasis, honeycombing, and emphysema. When pulmonary cysts are encountered in older children or adult patients, a number of specific disorders, collectively referred to as diffuse cystic lung diseases, merit consideration. These conditions include Langerhans cell histiocytosis, lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, follicular bronchiolitis, and lymphocytic interstitial pneumonia, and even light-chain deposition disease and amyloidosis. More recently, etiologies of small airway obstruction, including asthma, hypersensitivity pneumonitis, and bronchiolitis obliterans, have been reported to cause diffuse cystic lung disease. When diffuse cystic pulmonary disorders are encountered, the combination of the clinical history, presentation, and the imaging appearance of the pulmonary cysts may be sufficiently characteristic to offer a specific diagnosis. However, not infrequently, tissue sampling procedures are required to establish the correct diagnosis because the imaging features of diffuse cystic pulmonary disorders may overlap. Distinguishing among the various etiologies of diffuse pulmonary cysts is important because the treatment approaches to these conditions differ substantially.
Department of Radiology, Mayo Clinic, Arizona, Phoenix, AZ
Disclosure: The authors declare that they have no conflicts of interest.
Address correspondence to: Michael B. Gotway, MD, Department of Radiology, Mayo Clinic, Arizona, 5777 East Mayo Blvd., Phoenix, AZ 85054. E-mail: firstname.lastname@example.org.