Table 1.
Common reactive histologic patterns in CTDs.
| Compartment | Histologic pattern | Histopathological findings |
|---|---|---|
| Alveolar parenchyma | Fibrotic NSIP | Diffuse temporally uniform fibrosis with little associated chronic inflammation |
| UIP | Non-uniform fibrosis with honeycomb change, fibroblast foci, mild inflammation | |
| OP | Plugs of loose connective tissue (Masson bodies) in distal airway lumens and alveolar spaces | |
| DAD | Alveolar wall edema and hyaline membranes in acute DAD, organization (OP) in airspaces and alveolar walls in organizing DAD | |
| LIP | Dense infiltrate of small lymphocytes, plasma cells, small clusters of epithelioid histiocytes, multinucleated giant cells that diffusely involves the distal parenchyma and markedly widens alveolar walls | |
| CIP | Mild diffuse interstitial infiltrate of chronic inflammatory cells that are considerably less dense than in LIP | |
| Lymphoid hyperplasia | Lymphoid aggregates and follicles with germinal centers throughout biopsy with/without follicular bronchiolitis | |
| Alveolar hemorrhage | Airspace red blood cells in acute hemorrhage, airspace macrophages with coarsely granular hemosiderin in chronic hemorrhage | |
| Pleura | Pleuritis | Acute and/or organizing fibrinous pleuritis, fibrous pleuritis, edema, variable chronic inflammation with/without germinal centers |
| Airways | Bronchitis/bronchiolitis | Prominent chronic and occasionally acute inflammatory cell infiltrate in walls of small airways |
| Follicular bronchiolitis | Lymphoid follicles containing prominent reactive germinal centers confined to the peribronchiolar interstitium | |
| Constrictive bronchiolitis | Subepithelial fibrosis causing luminal narrowing or luminal obliteration by fibrous tissue | |
| Vessels | Pulmonary hypertension | Spectrum from mild muscular hypertrophy and intimal thickening to severe concentric intimal fibrosis, luminal occlusion, plexiform and dilation lesions, and rarely fibrinoid necrosis and necrotizing arteritis |
| Vasculitis | Mural infiltrates of monocytes/histiocytes and neutrophils predominate | |
| Capillaritis | Necrotizing acute inflammation of alveolar wall capillaries |
NSIP: non-specific interstitial pneumonia; UIP: usual interstitial pneumonia; OP: organizing pneumonia; DAD: diffuse alveolar damage; LIP: lymphoid interstitial pneumonia; CIP: cellular interstitial pneumonia.
Modified from pp 587–596, Colby 1998.