Cystic and Cavitary Lung Disorders

A “cystic lesion” is a nonspecific term used to describe an area of decreased lung opacity identified radiologically (1–4). These lesions can be focal or multifocal, bilateral or sometimes unilateral. The lesion should be distinguished from air-trapping caused by pathologies of the bronchus or blood vessels, and from a decrease in opacity due to mosaic perfusion. According to the definition by Webb et al., a cystic airspace is a thin-walled (usually < 3 mm), well-circumscribed, air-containing lesion with a diameter of 1 cm or more, and must be visible on high resolution computed tomography (HRCT) (3,4). The definitions with respect to the size and wall thickness are arbitrary, and there has been no consensus on the differentiation of a cystic lesion from other pathologic lesions with decreased lung opacity, such as cavities.