Focal organizing pneumonia: CT and pathologic findings

The purpose of this study was to describe the CT findings of focal organizi ng pneumonia and to compare the findings with pathology. CT findings of his tologically proven focal organizing pneumonias in 26 consecutive patients w ere analyzed. In 17 patients who had undergone surgical resections, the fin dings were correlated with pathology. Focal organizing pneumonias appeared as a nodule (n= 13) or a mass (n=13), ranging from 9 mm to 66 mm in diamete r. Ground-glass opacity was seen in 6/13 (46%) nodules and 6.5/13 (50%) mas ses (k=.48) with an extent ranging from 5% to 75% (mean, 16%). In 4/26 (15% ) patients, the extent was more than 50% of the lesion. They showed smooth (n=4), lobulated (n=8), spiculated (n=1), or lobulated and spiculated margi n (n=13). On correlative analysis, nodule or mass on CT consisted histologi cally of intraalveolar exudate or microabscess, chronic inflammatory cell i nfiltration, fibrotic nodules, and polypoid granulation tissue in the alveo lar or bronchiolar spaces. Ground-glass opacity consisted of interstitial f ibrosis and chronic inflammatory cell infiltration and intraalveolar polypo id granulation tissue. Focal organizing pneumonia may simulate a lung cance r with variable appearances on CT and the findings reflect underlying histo pathology of the disease.