Case of round pneumonia: pulmonary infarct and a rare situation that is similar with the lung cancer.

BACKGROUND AND AIMS: Round pneumonia (RP) is a rare radiological presentation of a subtype of lobar pneumonia that arises because of a developmental defect in connective tissues (pores of Köhn and channels of Lambert). The round appearance on chest X-ray (CXR) is thought to occur from an infectious process that spreads from small peripheral alveoli centrifugally through interalveolar channels via the pores of Kohn and the canals of Lambert. This explains the nonsegmental distribution and shape of RP. The pathogenesis of RP is unknown. An alternative theory holds that RP in children occurs because of underdeveloped pores of Kohn and the absence of canals of Lambert, limiting the spread of the organism and resulting in a focal, round mass seen on radiographs. As a result of this developmental defect, dissemination of infection remains in a limited area. While this is a well-known entity in childhood, it has been described infrequently in adults. Lesions of RP are not necessarily round; oval lesions can also be seen. It is a radiological subtype of the pneumonia subtype and presents as a solitary nodule or a mass lesion in CXR.

METHODS: We presented two cases of RP. One mimicked and was mistaken for pulmonary infarction because of triangular pleural-based density and the other mimicked pulmonary malignancy because of a homogeneous triangular opacity based on the pleura on the posteroanterior radiography and computed tomography.

CONCLUSION: These cases were presented because of RP's importance, and RP should be considered a part of differential diagnosis of pulmonary infarct and lung tumor.