Pulmonary sarcoidosis: typical and atypical manifestations at high-resolution CT with pathologic correlation.

Sarcoidosis is a multisystem disorder that is characterized by noncaseous epithelioid cell granulomas, which may affect almost any organ. Thoracic involvement is common and accounts for most of the morbidity and mortality associated with the disease. Thoracic radiologic abnormalities are seen at some stage in approximately 90% of patients with sarcoidosis, and an estimated 20% develop chronic lung disease leading to pulmonary fibrosis. Although chest radiography is often the first diagnostic imaging study in patients with pulmonary involvement, computed tomography (CT) is more sensitive for the detection of adenopathy and subtle parenchymal disease. Pulmonary sarcoidosis may manifest with various radiologic patterns: Bilateral hilar lymph node enlargement is the most common finding, followed by interstitial lung disease. At high-resolution CT, the most typical findings of pulmonary involvement are micronodules with a perilymphatic distribution, fibrotic changes, and bilateral perihilar opacities. Atypical manifestations, such as masslike or alveolar opacities, honeycomb-like cysts, miliary opacities, mosaic attenuation, tracheobronchial involvement, and pleural disease, and complications such as aspergillomas, also may be seen. To achieve a timely diagnosis and help reduce associated morbidity and mortality, it is essential to recognize both the typical and the atypical radiologic manifestations of the disease, take note of features that may be suggestive of diseases other than sarcoidosis, and correlate imaging features with pathologic findings to help narrow the differential diagnosis.