CT halo sign in pulmonary metastases from mucinous adenocarcinoma of the pancreas.

The CT halo sign was first described in immunocompromised patients with invasive pulmonary aspergillosis. Although the halo sign was originally thought to be specific for invasive pulmonary aspergillosis, it has been reported in a wide variety of pulmonary abnormalities in both immununocompromised and immunocompetent patients. We report a case of mucinous adenocarcinoma of the pancreas metastatic to the lungs in which there were multiple pulmonary nodules showing the halo sign. This case further illustrates the nonspecific nature of the CT halo sign and the need to consider malignancy as a cause in immunocompetent patients.