Focal organizing pneumonia mimicking small peripheral lung adenocarcinoma on CT scans.

The present report of four cases highlights the potential for focal organizing pneumonia (FOP) to masquerade as a small peripheral lung adenocarcinoma on CT scans. Both entities may present the CT appearance of a peripheral spiculated lung nodule, often with an air bronchogram. A history suggestive of an infectious aetiology and the presence of other foci of inflammatory change on CT scan may be helpful clues to the diagnosis of FOP. Because FOP is comparatively rare, surgical excision will usually be required to exclude malignancy. In some cases, however, particularly after a negative percutaneous biopsy, conservative management with a follow-up CT scan at 3-4 weeks may be an alternative to immediate surgical intervention.