Case 20
Section 1
Clinical history: This 77-year-old, non-smoker had a cough and progressive dyspnea for one year at the time of the first HRCT (images 1 & 2). He received treatment with corticosteroids before the second HRCT (images 3 & 4) taken 3 months later.
Look at images 1 & 2.
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What are the abnormalities on the first HRCT (images 1 & 2)? a) interlobular septal
thickening Note the traction bronchiectasis. | ||||||||
Image 2--First HRCT
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Compare images 1 & 2 above with images 3 & 4. What changes have occurred after treatment? | ||||||
Image 4--Second HRCT
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The first HRCT images (1 & 2) are remarkable for the "blackness" of air in the bronchi, making them stand out against the surrounding lung parenchyma, which is affected by mild, diffuse ground-glass opacity. The follow-up HRCT images (3 & 4) (photographed using the same technique) show resolution of the ground-glass opacity. As a result, bronchi do not stand out so much as on the initial examination.
Section 2
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Traction bronchiectasis results in irregular bronchial dilation, often with distortion of the bronchial course and caliber. When seen in longitudinal section, bronchi may appear "beaded." Find an example of traction bronchiectasis in the left lung. Find and outline an example of reticular change in the right lung.
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Traction bronchiectasis results from alveolar collapse and/or fibrosis, causing irregular, focal or generalized traction on the airways.
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Find an example of traction bronchiectasis in the left lung. Find and outline an example of reticular change in the right lung. | ||||||
Reticular change is associated with interstitial lung disease and corresponds to areas of granulation tissue or fibrosis. Reticulation is most often seen in the subpleural lung. With progression, it may be replaced by honeycombed spaces, which appear as subpleural rows of thin-walled, air-filled circles (cysts), ranging from a few millimeters to several centimeters in diameter.
Section 3: Histologic Examples of Reticular Change and Ground-Glass Opacity
A section from the open lung biopsy of this man's lung shows nodules and strands of interstitial thickening within the lobule, corresponding to the reticular pattern seen on HRCT. This thickening has no constant relationship to anatomic structures such as airways, vessels, or interlobular septa.
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Find an almost normal interlobular septum showing slight edema. Find a normal pulmonary vein surrounded by dilated lymphatics. Find a centrilobular bronchovascular bundle. Find irregularly thickened pleura. Find two strands of irregular, intralobular interstitial thickening. Find a lymphoid aggregate. | ||||||||||
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Another area also shows the random pattern of involvement of the lobule. The inflammatory reaction is temporally homogeneous; i.e., each infiltrate is at the same stage of development. Ground-Glass Opacity Ground-glass opacity results from interstitial thickening and/or alveolar exudate. The edematous interlobular septum and the thinner interstitial infiltrates would have a ground-glass opacity whereas the larger infiltrates correspond to reticular change. Note that architectural distortion is absent.
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Although you cannot see cellular detail, what types of cells make up the interstitial infiltrate of the reticular change? Find an area of mild interstitial thickening that may contribute to ground-glass opacity rather than reticular change. Given the marked resolution of the changes on the HRCT, much of this infiltrate is reversible. | ||||||||||
Differential diagnosis of ground-glass opacity and reticular change on HRCT: Non-specific interstitial pneumonia, desquamative interstitial pneumonia, acute interstitial pneumonia, bronchiolitis obliterans organizing pneumonia, chronic eosinophilic pneumonia, and Churg-Strauss syndrome. Ground-glass opacity with some consolidation can be seen with usual interstitial pneumonia, but is atypical.
Diagnosis: Non-specific interstitial pneumonia
Histologic differential diagnosis: Collagen vascular disease, hypersensitivity pneumonia, drug reaction, resolving acute lung injury, infection (AIDS), usual interstitial pneumonia (non-representative biopsy), and idiopathic non-specific interstitial pneumonia [1]
Diagnostic features of non-specific interstitial pneumonia on HRCT [2]
References
1. Katzenstein AA, Myers JL. Idiopathic pulmonary fibrosis. Clinical relevance of pathologic classification. Am J Respir Crit Care Med. 1998; 157:1301-1315.
2. Park J, Lee K, Kim J, Park C, Suh Y, Choi D, Kim K. Nonspecific interstitial pneumonia with fibrosis: radiographic and CT findings in seven patients. Radiology 1995; 195:645-648.
c) Ground-glass
opacity
d) Reticular change
Post-treatment, the ground-glass opacity resolved, and the reticular change became less apparent. However, the traction bronchiectasis did not resolve.
Lymphoid cells, fibroblasts, and collagen. This infiltrate differs from early granulation tissue, which has abundant intercellular matrix.
Slightly edematous interlobular septum
Vein surrounded by dilated lymphatics in interlobular septum
Centrilobular bronchovascular bundle at a bifurcation
Irregular, intralobular interstitial thickening
Probable ground-glass rather than reticular opacity because of size
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