The comet tail sign is a finding that can be seen on CT scans of the chest. It consists of a curvilinear opacity that extends from a subpleural "mass" toward the ipsilateral hilum. The comet tail sign is produced by the distortion of vessels and bronchi that lead to an adjacent area of round atelectasis, which is the mass. The bronchovascular bundles appear to be pulled into the mass and resemble a comet tail.
Adjacent pleural thickening is almost always seen and well demonstrated at CT. On administration of IV contrast, homogenous enhancement is seen. This, however may also be seen in carcinomas and hence cannot be used as a differentiating feature.
It should not be confused with: