Evaluation of CT appearances of localized organizing pneumonia (OP)

CT appearances of 12 cases with localized organinzing pneumonia (OP) were analyzed. OP could he classified into three groups. One group (n=6) was a round mass lesion. Another group (n=3) was a bandlike mass lesion along the bronchovascular bundle (BVB). The other group (n=3) was a band-like mass lesion along the pleura. The band like shapes along the BVB or the pleura were thought to be particular in OP. In all cases, the margin of OP was concaved to contiguous normal lung, and on HRCT, the margin was separated by intra-lobar septa. Air bronchogram, pleural indentation, wall thickening or dilatation of involved bronchus were often found in OP. Especially, the appearances of the margin separated by intra-lobar septa and wall thickening or dilatation of involved bronchus could be useful for differentiation from peripheral lung cancer.