Radio-pathological correlation of organizing pneumonia (OP): a pictorial review

Abstract

Since the description of cryptogenic organizing pneumonia in 1983 by Davison et al and the subsequent report on bronchiolitis obliterans organizing pneumonia by Epler et al, some reports have been published regarding the imaging features of organizing pneumonia (OP). In this pictorial review, we aimed to describe and illustrate different manifestations of OP on high-resolution CT (HRCT) accompanied by their histopathological correlations for a better comprehension of pathomechanism of the radiological findings. The main HRCT findings in OP include: consolidation, ground-glass opacification, perilobular opacity, reversed halo opacity, nodule or mass, parenchymal bands, bronchial wall thickening, bronchial dilatation, mediastinal lymphadenopathy and pleural effusion. In addition, we discuss the radiological differential diagnosis for each manifestation, as well as imaging evolution during patient follow-up, and two OP-related entities: the possibility of non-specific interstitial pneumonia development following OP and a relatively new rare entity related to OP called acute fibrinous and organizing pneumonia. For radiologists and physicians, a detailed knowledge of the potential radiological manifestations in OP is crucial for making a correct diagnosis and managing the patient properly. Moreover, some unnecessary lung biopsies will be avoided.

Figure 1.

Consolidation in organizing pneumonia: peripheral consolidation (within the box) with air bronchogram (arrow) and areas of bubbly lucencies (asterisk) is noted in right lower lobe.

Figure 2.

Histopathologic correlation for Figure 1: a Masson body is seen in the intra-alveolar space (within the box). There is also mild infiltration of inflammatory cells in the interlobular septa (arrows) (haematoxylin and eosin stain, ×200).

Figure 3.

Ground-glass opacity (GGO) in organizing pneumonia: bilateral patchy GGOs (arrows) are seen in parahilar regions.

Figure 4.

Histopathologic correlation for Figure 3: intra-alveolar granulation tissue and desquamated cells (within the box) along with interlobular septal inflammation (arrows) is seen (haematoxylin and eosin stain, ×200).

Figure 5.

Reversed halo (Atoll sign) in organizing pneumonia (OP): a peripheral mass in right lung base with reversed halo sign (arrow). The mass was biopsied, and the histopathologic study revealed it to be OP.

Figure 6.

Nodular pattern of organizing pneumonia (OP): randomly distributed nodules (arrows) are seen in both lung fields. Histopathologic result was OP.

Figure 7.

Parenchymal bands in organizing pneumonia (OP): parenchymal bands (white arrows) are seen in both lungs projecting from the visceral pleura towards the lung parenchyma in the follow-up high-resolution CT of a patient with OP. These bands are usually up to 5 cm in length and 1–3 mm in thickness. In addition, subpleural band-like reticulations (black arrows) are noted in right lung base, which may be suggestive of non-specific interstitial pneumonia development.

Figure 8.

Bronchial wall thickening, bronchial dilatation and perilobular opacity in organizing pneumonia: peribronchial wall thickening (asterisk) and bronchial dilatation (long arrow) is noted in right middle lobe within areas of consolidation and ground-glass opacity. Also, perilobular opacities (short arrows) are evident in the subpleural regions.

Figure 9.

Histopathologic correlation for Figure 8: a dilated bronchus (between arrows) is evident (haematoxylin and eosin stain, ×200).

Figure 10.

Follow-up CT scans in organizing pneumonia: (a) the initial chest CT scan is revealing two round well-defined opacities with reversed halo appearance (arrows) in both lung bases. (b) 20 days later, the patient was referred for CT-guided transthoracic lung biopsy. At that stage, lesions had been resolved centrally revealing a typical “Atoll sign” (arrows). (c) 22 days after the second scan, another chest CT scan was performed. There was no significant improvement. (d) Approximately 100 days after the third scan, the follow-up high-resolution CT showed none of the lesions, and there was no evidence of any residual disease in both lungs.

Figure 11.

Organizing pneumonia (OP) and cellular non-specific interstitial pneumonia (NSIP): bilateral band-like interlobular/intralobular reticulations (arrows) parallel to the chest wall with subpleural sparing in a patient with prolonged OP in favour of cellular NSIP.

Figure 12.

Histopathologic correlation for Figure 11: marked interstitial inflammation consistent with cellular non-specific interstitial pneumonia (haematoxylin and eosin stain, ×200).

Figure 13.

Organizing pneumonia and fibrotic non-specific interstitial pneumonia (NSIP): bibasilar subpleural interlobular/intralobular reticulation along with tractional bronchiolectasis in favour of fibrotic NSIP.

Figure 14.

Histopathologic correlation for Figure 13: areas of interlobular fibrosis (asterisks) and histopathologic honeycombing (between arrows) is seen (haematoxylin and eosin stain, ×200).

Figure 15.

Acute fibrinous and organizing pneumonia: (a) confluent consolidation (within the box) and patchy ground-glass opacities (more in the right lung) with posterior predominance in a patient admitted in the intensive care unit. (b) Follow-up CT scan 15 days later shows partial resolution with bilateral subpleural intralobular reticulations (long white arrows) with a short distance of subpleural sparing (short black arrows).

Figure 16.

Histopathologic correlation for Figure 15: an intra-alveolar Masson body (within the box) and fibrin strands admixed with inflammatory cells (arrows) is seen (haematoxylin and eosin stain, ×200).