Case 10

Section 5

Histologic Findings

This view of an entire section shows several long, thin, parenchymal bands, as well as thickening of the bronchovascular interstitium. More detail is shown below. Trichrome stain (collagen is green)

Parenchymal Band

At higher magnification of the above section, deposition of collagen in a long, thin, parenchymal band can be seen. The alveolar parenchyma is mostly normal. Centrilobular interstitium is also fibrotic (see below).

Find and follow a long, fibrotic parenchymal band that spans several lobules.


Centrilobular Nodules

At higher magnification of the section above, two regions of centrilobular fibrosis can be seen.

Find the two regions of centrilobular fibrosis.

In time, this fibrosis and that in the interlobular septum will radiate in an irregular fashion into the lobule to cause lobular architectural distortion with centrilobular to interlobular septal bridging and lobular shrinkage.


Lobular Remodeling

This entire section (detailed below) shows more advanced interstitial fibrosis with bridging from interlobular septa to bronchovascular interstitium and distortion of the lobule. Note that the more central lung parenchyma is spared. (Trichrome stain for connective tissue)

Lobular Remodeling, continued

This H&E-stained section shows the result of prolonged subpleural, interlobular septal, and centrilobular fibrosis. The fibrosis has distorted the lobular architecture and linked centrilobular and interlobular septal structures. Inflammatory cells are sparse.

Find an example of a bronchiolovascular bundle. Note how it is connected to a thickened interlobular septum to its left.

Find a portion of an interlobular septum with a vein cut longitudinally.

Note areas of subpleural fibrosis.

The radiating fibrosis in the right lower quadrant (outline it) represents linked lobular and interlobular septal fibrosis.


Centrilobular Nodules

Here, peribronchiolar fibrosis, which represents a centrilobular nodule on HRCT, is present. Nearby peribronchiolar air spaces have been obliterated, but more distal ones are intact.

Find the bronchiolar lumen.

Find the pulmonary artery.

Find 2 collections of brown pigment in air spaces.

What does the pigment represent?





Case 10--Continued

Table of Contents




























Long, fibrotic parenchymal band that spans several lobules





























Centrilobular fibrosis





























Bronchiolovascular bundle





























Longitudinally cut vein in fibrotic interlobular septum






























Radiating fibrosis, septal and intralobular
































Bronchiolar lumen




























Pulmonary artery































Brown pigment in alveolar space




























Collections of hemosiderin pigment. Diagnostic structures (see next page) may sometimes be found here. Hemosiderin pigment is also present in the peribronchiolar scar.