Interstitial Pneumonias

Non-specific interstitial pneumonia (NSIP)

Features are:

  • Patchy interstitial inflammation
  • Variable interstitial fibrosis
  • Rare architectural distortion
  • Rare fibroblast foci
  • Inconspicuous BOOP-like changes
  • Occasional, ill-defined granuloma

Here, normal lung and mild, cellular interstitial pneumonia are mixed.

See also Case 27

Rheumatoid nodules

Pulmonary changes in collagen-vascular diseases frequently include NSIP. Other changes are bronchiolitis and vascular abnormalities. Occasionally, the lung in patients with rheumatoid arthritis will show rheumatoid nodules.

Here, two nodules with palisading histiocytes and multinucleated giant cells surround a central zone of necrosis.

Hypersensitivity pneumonia

Features include:

  • Lymphocytes and plasma cells that infiltrate bronchiolovascular bundles and scattered areas in alveolar walls (alveolitis)
  • Small, ill-defined granulomas

The late stage resembles UIP, but may have granulomas.

TB = terminal bronchiole

RB = respiratory bronchiole

AD = alveolar duct

The granulomas often have cholesterol clefts--the slit-like spaces that contained lipid before it was dissolved in the tissue processing. Sometimes Schaumann bodies and endogenous, birefringent crystals are also present.

See also Case 18