Table 3 The six histopathological patterns of diffuse lung diseases
Pattern 1 (acute lung injury)Pattern 2 (fibrosis)Pattern 3 (cellular infiltrates)Pattern 4 (alveolar filling)Pattern 5 (nodules; small or large, single or multiple)Pattern 6 (minimal changes)
  • Diffuse alveolar damage (any cause; see box 1)

  • Pneumoconioses

  • Hypersensitivity pneumonitis (subacute disease)

  • Pulmonary oedema

  • Neoplasms (primary or metastatic)

  • Pulmonary oedema

  • Infections

  • Usual interstitial pneumonia

  • Drug reactions

  • Acute bronchopneumonia

  • Granulomatous infections (see box 7 for causes of granulomas in biopsy specimens)

  • A very subtle interstitial infiltrate

  • Drug reactions

  • Chronic hypersensitivity pneumonitis

  • Related to rheumatic diseases

  • Acute eosinophilic pneumonia

  • Pneumoconioses (especially silica-related)

  • Pulmonary emboli (including fat emboli)

  • Related to rheumatic disease

  • Related to rheumatic disease

  • Lymphoproliferative diseases

  • Unusual infections with prominent histiocytes (eg, Rhodococcus equi)

  • Aspiration

  • Constrictive bronchiolitis

  • Related to toxins, fumes and gases

  • Chronic drug reactions

  • Non-specific interstitial pneumonia

  • Alveolar haemorrhage

  • Nodular drug reaction (eg, amiodarone)

  • Vasculopathic diseases

  • Acute eosinophilic pneumonia (see box 2)

  • Advanced sarcoidosis

  • Certain infections (eg, rickettsia, mycoplasma, HIV)

  • Desquamative interstitial pneumonia (DIP; see box 6 for causes of DIP-like reactions)

  • Sarcoidosis/berylliosis

  • Cystic diseases

  • Alveolar haemorrhage syndromes (see box 3)

  • Fibrotic non-specific interstitial pneumonia

  • Lymphoid interstitial pneumonia

  • Respiratory bronchiolitis-associated interstitial lung disease

  • Langerhans cell histiocytosis

  • Lymphangioleiomyomatosis

  • Transplant rejection

  • Chronic aspiration

  • Organising pneumonia (any cause; see box 5)

  • Wegener granulomatosis

  • Langerhans cell histiocytosis

  • Idiopathic forms (acute interstitial pneumonia and “acute fibrinous and organising pneumonia”)6

  • Chronic radiation injury

  • Organising pneumonia (cryptogenic)

  • Persistent organising pneumonia

  • Sampling error

  • Advanced Langerhans cell histiocytosis

  • Alveolar proteinosis

  • Pulmonary hyalinising granuloma

  • Hermansky–Pudlak syndrome

  • Acute fibrinous and organising pneumonia (cryptogenic)

  • Plasma cell granuloma

  • Erdheim–Chester disease (non-Langerhans cell histiocytosis)

  • Dendrifom calcification

  • Lung infarct

  • Idiopathic airway-centred fibrosis

  • Alveolar microlithiasis

  • Rosai–Dorfman disease