"Tree-in-Bud" Pattern, Centrilobular Nodules, and Parenchymal Opacities

A closer look at the HRCT of the Lady Windermere syndrome shows more detail. Click here for further explanation.

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Figure 1. HRCT Findings

Note the faint interlobular septa delineating the lobules.

Find 2 centrilobular nodules.

Find 2 "tree-in-bud" patterns. Click here to see histologic example.

Find 2 clusters of centrilobular nodules (rosettes). Click here to see histologic example.

Find a larger parenchymal opacity along the fissure in the left lower lobe.

 

Figure 2. Normal Lobule

The pulmonary lobule (or secondary lobule) is composed of several acini, each with a bronchiolo-arterial bundle and its alveoli. Here, parts of 2 acini with their bronchiolo-arterial bundles are shown. The lobules are separated by interlobular septa, which contain the pulmonary veins. The larger spaces in the alveolar parenchyma represent alveolar ducts.

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Find the interlobular septum.

Find two bronchiolo-arterial bundles.

Find an alveolar duct in the right quarter of the image.

Centrilobular nodules correspond to lesions in or around the bronchioles. The "tree-in-bud" pattern represents a bronchiolar lesion including a branch point. Clusters of nodules (rosettes) may represent several bronchiolar nodules in one lobule or several small, clustered, parenchymal nodules.

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Bronchocentric Granuloma

Here, an airway (marked by the pulmonary artery and two small residual lumens) has been almost completely obliterated by granulomatous inflammation, represented by a few multinucleated giant cells, fibroblasts, and a lymphoid infiltrate. Note that the inflamed area (lumen, airway wall, and surrounding tissue) exceeds the size of the previous bronchiole (bronchiole and artery should be the same size).

 

When this lesion involves a branch point, as shown here, and the parent bronchiole, it corresponds to the "tree-in-bud" pattern on HRCT.

 

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Conglomerate Nodules (Rosettes on HRCT)

Coalescence of granulomas (the rounded pink structures) has occurred here to form a larger mass or rosette, 1.3 cm in diameter. Note the multiple dilated bronchioles (large white spaces) with little inflammation in their walls and several non-dilated bronchioles with more mural inflammation. The intervening lung parenchyma shows patchy scar.

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Bronchiolo-arterial bundle

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Alveolar duct

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Centrilobular nodule

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Tree-in-bud pattern

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Clustered centrilobular nodules (rosette)

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Parenchymal opacity

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