Minute Meningothelial-Like Nodules

Figure 1. Early Lesion

This proliferation of several layers of cells around a vein represents an early lesion.

Figure 2. Detail of Nests: In well-developed lesions, whorled nests of cells are arranged in concentric layers around small veins, which may become obliterated. Capillaries are frequent within the nodules.

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Find 2 nests of cells with patent small central vessels.

Find 2 nests of cells with obliterated central vessels.

Note again the layer of capillaries facing the air spaces.

Figure 3. Edge of Lesion: Isolated clusters of cells may be found separated from the main mass.

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Find two clusters of cells separate from the main mass.

Destruction of alveolar walls occurs around these masses creating a paranodular emphysema. In this case, a number of pyknotic inflammatory cells including PMNs are present in an alveolar wall near the center of the image. This capillaritis may cause the disruption of the alveolar wall.

Find the alveolar wall with inflammatory cells.

 

Note the rounded nests of whorled cells at the bottom of the image.

Figure 4. Fibrotic Lesion

With time, fibrosis develops, obliterating the cellular nests. Here, perivascular fibrosis has replaced much of the nodule.

Click here to see the ultrastructure.

 

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Nest with patent central vein

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Nest with obliterated central vein

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Cell cluster away from main mass. Note that the cell borders are so ill-defined that the cells appear as multinucleated giant cells.

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Inflammatory cells in alveolar wall adjacent to nodule

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