Histologic Changes

Temporal changes

In some areas, the sections showed loose, edematous connective tissue with a bluish matrix (fibroblast foci) containing spindled fibroblasts and a number of lymphoid cells. Compare this appearance with the denser, less cellular, pink connective tissue at the lower left. What does the juxtaposition of these two types of connective tissue mean about the time course of the disease? Answer

Temporal changes--Elastic van Gieson stain

The dark red indicates mature collagen (left arrow), whereas the paler pink with spindled fibroblasts (right arrow) represents newly formed connective tissue (a fibroblast focus). It begins as organization of alveolar exudate but gradually becomes incorporated into the interstitium and reepithelialized. Note the very thin, new epithelium over this connective tissue near the bottom of the picture. Elastic tissue is black with this stain.

Vascular changes

Vessels in the vicinity of the inflammation show narrowing of their lumens by a proliferation of myointimal cells derived from the muscular media. Here, the thin media (arrowheads) is separated from the lumen by a rather thick myointimal layer. Note the scattered bundles of metaplastic smooth muscle in the widened interstitium (arrow).

As a result of the progressive interstitial fibrosis, the capillary bed is also diminished.

Clinical summary Image 4

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Answer: Recent fibroblastic, granulation tissue and old fibrosis together indicate temporal heterogeneity of progressive disease.

Clinical summaryImage 4

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