Rounded atelectasis with atypical computed tomography findings.

Rounded atelectasis is atelectasis of the peripheral part of the lung, typically in contact with thickened pleura, featuring characteristic computed tomography findings. In this case, a 61-year-old man with history of asbestos exposure presented with a right-middle-lobe nodule on chest radiograph, with computed tomography findings suspicious for neoplasm. The patient underwent surgical resection, which revealed rounded atelectasis. Our case raises a question about the sensitivity of radiographic criteria used in identifying rounded atelectasis, and it emphasizes the need to keep rounded atelectasis in the differential diagnosis of a single pulmonary nodule in a patient with a history of asbestos exposure.