IS Case 428: Round pneumonia
Imaging Sciences URMC 2010
Publication Date: 2010-08-27
Patient is a 51-year-old male presenting with night sweats, malaise and chest discomfort.
CT and radiographs demonstrate a 4.7 x 4.8 cm heterogeneous, rounded, peripheral mass in the right middle lobe with a lobulated low attenuation center. Follow-up radiograph 6 weeks later demonstrates resolution of the mass.
Round pneumonia is an uncommon infectious process in adults who may present with viral symptoms, hemoptysis or asymptomatically. The process was first described in 1954 and is typically distinguished from malignant pathologies by rapid expansion or resolution. This infection was initially thought to represent a localized centrifugal spread of bacteria through canals of Lambert and pores of Kahn. However, more recent theorizes suggest that this process may represent a focal proliferation of organisms that cannot spread to adjacent parenchyma secondary to blocked or incompletely developed canals of Lambert and pores of Kahn. This would explain the higher prevalence of round pneumonia in children. Typical etiologies include S. pneumonia, K. pneumonia, H. influenza and M. tuberculosis.
Round pneumonias may present as large masses with a diameter of 5 cm to 7 cm and must be distinguished from bronchogenic carcinoma. Air bronchograms within the lesion were once thought to indicate malignant disease, but this association has been disputed. Round pneumonias can less commonly have spiculated appearances, satellite lesions, associated pleural thickening and heterogeneous uptake, making the diagnosis difficult. Distinguishing factors include infectious symptoms at presentation, middle and lower lobe predominance, and rapid resolution with antibiotics.
These pneumonias were once thought to be present in only 1% of adult cases, however their prevalence is suggested to be higher. The majority of these pneumonias are likely treated before radiographs are obtained and CT scans or chest radiographs may be obtained and read before all of the clinical data is available to make the diagnosis. They should therefore routinely be incorporated into the differential diagnosis for benign mass lesions.
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