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# Nonspecific interstitial and cryptogenic organizing pneumonia

- Lesion

Two interstitial patterns with a better outlook than IPF: NSIP is even inflammation or fibrosis; organizing pneumonia is fibroblast plugs in airspaces.

Updated Nov 12, 2026

## Key points

- NSIP: cellular or fibrosing pattern; lesions of the same age (temporal homogeneity); no fibroblastic foci or honeycombing.
- NSIP is the commonest lung pattern in systemic sclerosis and is common in other connective tissue diseases.
- Organizing pneumonia: polypoid plugs of loose fibroblastic tissue (Masson bodies) in alveolar ducts, alveoli and bronchioles; lung architecture preserved.
- Organizing pneumonia follows infections, toxins, drugs, connective tissue disease and graft-versus-host disease; COP when cryptogenic.
- COP: cough, dyspnoea, patchy subpleural or peribronchial consolidation; most patients need steroids, some recover spontaneously.

## What it is

Nonspecific interstitial pneumonia (NSIP) is diffuse, uniform interstitial inflammation, fibrosis or both, often in younger adults and frequently linked to connective tissue disease. Organizing pneumonia is a healing pattern in which plugs of loose granulation tissue fill alveolar ducts and alveoli; when no cause is found it is called cryptogenic organizing pneumonia (COP). Both respond better to treatment than UIP.

## Structure

- Cellular NSIP: mild to moderate interstitial infiltrate of lymphocytes and a few plasma cells, spread evenly.
- Fibrosing NSIP: diffuse or patchy interstitial fibrosis, all of the same age.
- Organizing pneumonia: rounded, pale, myxoid plugs of fibroblasts and myofibroblasts in airspaces, with normal alveolar walls between them.
- No hyaline membranes, granulomas or honeycombing in either.

## Step by step

- An insult (infection, drug, autoimmune attack) injures the alveolar wall or airspace.
- In NSIP, inflammation spreads evenly through the septa at one time, so any fibrosis is uniform in age.
- In organizing pneumonia, fibrin exudate in the airspaces is invaded by fibroblasts instead of being cleared.
- The fibroblasts form plugs (Masson bodies) that obstruct ducts and bronchioles.
- Because the scaffold is preserved, the plugs can be resorbed with treatment and the lung returns to normal.

## Markers

- Masson bodies

## Clinical notes

- NSIP: subacute dyspnoea and cough in middle-aged adults, often women and non-smokers; search for connective tissue disease.
- Cellular NSIP carries a much better prognosis than UIP; fibrosing NSIP is in between.
- COP mimics pneumonia that does not respond to antibiotics.

## Memory aid

NSIP is Neat and Synchronous; organizing pneumonia plugs the Passages.

## Test yourself

Think of the answer, then tap the question to see it.

## What histologic feature separates fibrosing NSIP from UIP?

Fibrosis in NSIP is uniform and of the same age, without fibroblastic foci or honeycombing.

## What are Masson bodies?

Polypoid plugs of loose organizing connective tissue (fibroblasts in a pale matrix) within alveolar ducts, alveoli and bronchioles, the mark of organizing pneumonia.

## When is an organizing pneumonia called cryptogenic?

When no cause such as infection, drug, toxin, connective tissue disease or graft-versus-host disease is identified.

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## Connections

## Related 4

- [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/)
- [Idiopathic pulmonary fibrosis (UIP pattern)](https://durgical.com/en/general-pathology/idiopathic-pulmonary-fibrosis/)
- [The lung in autoimmune disease](https://durgical.com/en/general-pathology/the-lung-in-autoimmune-disease/)
- [Diffuse alveolar damage (ARDS)](https://durgical.com/en/general-pathology/diffuse-alveolar-damage/)

## Related conditions 1

- [Interstitial lung disease](https://durgical.com/en/conditions/interstitial-lung-disease/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Interstitial Lung Disease](https://www.ncbi.nlm.nih.gov/books/NBK541084/) (StatPearls (NCBI Bookshelf), 2025); [Interstitial Lung Diseases](https://medlineplus.gov/interstitiallungdiseases.html) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/nonspecific-interstitial-and-cryptogenic-organizing-pneumonia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/nonspecific-interstitial-and-cryptogenic-organizing-pneumonia/