Rounded atelectasis: a pulmonary pseudotumor.

Rounded atelectasis is a benign entity that is often misinterpreted as a pulmonary neoplasm. The roentgenologic appearance of a mass is due to an infolding of atelectatic tissue intermingled with pleura, blood vessels, and bronchi. Rounded atelectasis is usually asymptomatic and is commonly associated with chronic pleural disease or pleural effusions. The distinctive radiologic features include a rounded, pleural-based opacity associated with adjacent pleural thickening and volume loss of the affected lobe. The pathognomonic sign is the "comet tail" that results from the crowding of vessels and bronchi as they enter the atelectatic region. Many authors consider this constellation of findings diagnostic. Rounded atelectasis usually remains stable over time; however, slow growth, as well as diminution in size, has been described. A retrospective analysis revealed 7 cases of rounded atelectasis at our institution over a 9-year period. Three were operated on to exclude malignancy, one was confirmed at operation performed for other reasons, and 3 were followed up expectantly. We conclude that recognition of this entity and its radiologic features can be diagnostic and render further workup, including thoracotomy, unnecessary.