Usual Interstitial Pneumonia
Definition
- Idiopathic interstitial lung injury demonstrating temporal and geographic heterogeneity
Alternate/Historical Names
- Cryptogenic fibrosing alveolitis
- Idiopathic pulmonary fibrosis
- UIP
Diagnostic Criteria
- Clinical
- Insidious onset of dyspnea, cough
- Most have symptoms >6 months
- Rare under age 40
- Pulmonary function tests: restrictive with decreased diffusing capacity
- UIP is relentlessly progressive
- Median survival 2.5-3.5 years
- Insidious onset of dyspnea, cough
- High resolution computed tomography (HRCT)
- Changes predominantly basal and peripheral
- Reticular, linear patterns, retraction bronchiectasis
- Honeycombing usually present
- Ground glass opacities focal but not widespread
- Classic cases can be diagnosed by xray and do not need biopsy confirmation
- Histopathologic features
- Heterogeneous pattern of alternating honeycombing and normal lung with intermediate zones of inflammation and active fibrosis
- Spatially heterogeneous fibrosis
- Patchy honeycombing and severe architectural distortion predominantly subpleural and paraseptal
- Enlarged, remodeled airspaces with thickened walls
- Usually filled with mucus
- Patchy honeycombing and severe architectural distortion predominantly subpleural and paraseptal
- Temporally heterogeneous fibrosis
- Ranges from loose fibroblastic foci (septal fibromyxoid foci) to dense fibrosis
- Foci of active fibroplasia next to mature collagenous scarring is characteristic
- Increased number of fibroblastic foci has been proposed as a poor prognostic sign
- Most studies in patients with clinically stable disease show no prognostic significance (Flaherty 2003, Hanak 2008)
- Ranges from loose fibroblastic foci (septal fibromyxoid foci) to dense fibrosis
- Interstitial lympho-plasmacytic infiltrate usually mild
- Organizing pneumonia may be present but not predominant
- Smooth muscle hyperplasia may be prominent
- The following features should not be present
- Features of hypersensitivity reaction
- Giant cells and or granulomas
- Predominantly bronchiolocentric distribution
- Features of other defined diseases such as:
- Langerhans cell histiocytosis
- Sarcoidosis
- Marked inflammation
- Marked eosinophilic infiltrate
- Foreign material, especially asbestos
- Patients with acute exacerbation may show a combination of features of diffuse alveolar damage (DAD)or cryptogenic organizing pneumonia and UIP
- Defining feature
of DAD
- Hyaline membranes, intact or organizing
- Features that should suggest superimposed DAD
- Squamous metaplasia of respiratory bronchioles
- Fibrin thrombi in small arteries
- Type II pneumocyte hyperplasia
- Intralumenal plugs of loose granulation tissue should suggest superimposed organizing pneumonia, cryptogenic or secondary to a known cause
- Clinical and radiographic history is important
- High mortality rate
- Defining feature
of DAD
- Discordant features may be seen (UIP on one biopsy, NSIP on another)
- Behaves as UIP
- Multiple biopsies are recommended, if possible
- The following must be ruled out in every case
- Collagen vascular disease
- Typically has more inflammation and follicles
- Typically less fibroplasia and honeycombing
- Drug reaction
- Infection
- Acid fast and fungal stain should be performed in every case
- Radiation effect
- Hermansky-Pudlak syndrome
- Pulmonary fibrosis, granulomatous colitis, albinism, platelet defect
- Collagen vascular disease
Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
