[Rounded atelectasis of the lung].

Rounded atelectasis is an uncommon but increasingly recognized form of pulmonary collapse that often mimics a pulmonary neoplasm. It is suggested that these lesions can occur many years after exposure to asbestos or exudative pleural effusions. The authors report 16 cases of rounded atelectasis seen during a period of over 10 years, 9 of which in the last 18 months. They describe the plain film, tomographic and CT appearances of the lesion. The radiographic features that allow a diagnosis are rounded or oval shadows lying along the posterior surface of the lower lobe, adjacent to thickened pleura. Lateral tomography and CT show the blood vessels and bronchi curving toward the mass and converging on one edge, like a comet tail. Differentiation of rounded atelectasis from neoplastic disease is essential in avoiding unnecessary thoracotomy.