Pathologic approach to cystic lung disease

Pulmonary cysts are commonly identified on imaging studies and frequently pose diagnostic problems in practice. For some patients, the imaging appearances are sufficiently characteristic to allow a confident diagnosis radiologically, whereas other patients may require surgical lung biopsy to identify the etiology of the cysts. For some cystic lung diseases, the histopathology is specific, and a diagnosis can be established either by pure morphology or with the aid of ancillary testing. Other cases require more thorough clinical, radiological, and pathologic evaluation for diagnosis. This article details the clinical presentation, imaging, and pathology findings of the 5 major diffuse cystic lung diseases in adults: lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, lymphoid interstitial pneumonia, Birt-Hogg-Dubé syndrome, and the cysts of honeycomb remodeling. More esoteric causes of pulmonary cysts are also reviewed. A surgical pathology-based approach to cystic lung disease is provided to aid the surgical pathologist in developing a differential diagnosis that can be further narrowed by incorporating imaging and clinical features.