Elementary Lesions
Elementary Lesions
Fibroblast focus
Temporal variability of fibrosis
Characteristics
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Localised focus of active, ongoing fibrosis
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Stretched out elongated structure of active fibrosis rich in myofibroblasts embedded within myxoid stroma
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Characteristic of usual interstitial pneumonia. Helps confirm the diagnosis
Diagnostic Orientation
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Topography
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At the expanding front of the fibrosis between the apparently normal lung and the established areas of fibrosis
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Orientation
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Parallel to the surface of the alveolar cavity
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Protrudes into the alveolar lumen
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1. Fibroblast focus
![Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-11%402x_2.png)
2. Fibroblast focus
![2. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-12%402x.png)
Collagen dense scar tissue, with a fibroblast focus stand out at low magnification
3. Fibroblast focus
![3. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-12%402x_0.png)
Mature inactive collagen disposition showing mild associated chronic lymphocytic infiltrate and typical fibroblast focus
4. Fibroblast focus
![4. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-13%402x.png)
Collagen fibrous scar with fibroblast focus protruding into the alveolar lumen at the expanding front of the fibrosis.
5. Fibroblast focus
![5. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-14%402x.png)
Fibroblast focus protruding into the alveolar lumen.
6. Fibroblast focus
![6. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-15%402x.png)
Fibroblast focus: myofibroblasts stretched out on loose collagen tissue.
7. Fibroblast focus
![7. Fibroblast focus](/dk/hrct/sites/default/files/2022-04/group-5-copy-16%402x.png)
The fibroblast focus is covered by base of flattened alveolar cells.