hypersensitivity pneumonitis: radiology and pathology aspect

PRESENTED IN RADIOLOGICAL-PATHOLOGICAL CONFERENCE

14 JULY 2015

BY T.CHAYOVAN

Hypersensitivity Pneumonitis: Essential Radiologic and

Pathologic Findings

Teri J. Franks, MD, Jeffrey R. Galvin, MD

Surgical Pathology Clinics

Volume 3, Issue 1, Pages 187-198 (March 2010) DOI: 10.1016/j.path.2010.03.005

Hypersensitivity pneumonitis

Diffuse granulomatous interstitial lung disease

Caused by an immunologic response to repeated aerosol

inhalation

Clinical, radiologic, and histologic findings are quite variable

Diagnosis depends on a constellation of findings rather than a single defining feature


Acute, subacute, or chronic

Significant overlap

Active versus residual


Radiologic triad

Centrilobular nodules, multifocal ground glass opacities, air trapping

Characteristic histologic triad

Airway-centered chronic interstitial inflammation

Interstitial poorly formed non-necrotizing granulomas

Organizing pneumonia

The recommendation of Schulyer

Symptoms compatible with hypersensitivity pneumonitis

Evidence of exposure to appropriate antigen

History or detection of serum and/or bronchoalveolar lavage (BAL) fluid

antibody

Findings compatible with hypersensitivity pneumonitis on chest

radiograph or HRCT

BAL fluid lymphocytosis

Histologic lung changes compatible with hypersensitivity pneumonitis

Positive natural challenge, which is reproduction of symptoms and

laboratory abnormalities after exposure to the suspected environment

Gross features

Gross specimens of large size are not often encountered

BAL, transbronchial biopsy, or surgical lung biopsy

Radiologic studies, particularly HRCT, as their in vivo gross lung

examination

Distribution of disease

Gross features

HRCT > plain chest radiograph

Sensitivity and specificity

Small, indistinct, centrilobular nodules

Multifocal ground glass opacities

Air trapping in the expiratory phase of respiration

Highly suggestive of hypersensitivity pneumonitis

Not specific: respiratory bronchiolitis, follicular bronchitis, and asthma

Fig. 1

Surgical Pathology Clinics 2010 3, 187-198DOI: (10.1016/j.path.2010.03.005)

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Fig. 3




Residual phase of hypersensitivity pneumonitis

Fibrosis

Reticular pattern, honeycombing, and traction bronchiectasis

Associated with reduced survival

These findings are most severe in the upper and middle lungs

Fibrosis similar to idiopathic pulmonary fibrosis (IPF)

Strikingly lower lobe predominance

Fig. 4




Fig. 5




Fig. 6




HP VS infection

Care for an infectious etiology

Focal or unilateral abnormalities

Fig. 7




Microscopic features

Not an atopic disease and is not associated with increased

eosinophils

Surgical lung biopsy > transbronchial biopsy

To appreciate the distribution of histologic findings of hypersensitivity pneumonitis

Microscopic features: Triad of active disease


Poorly circumscribed interstitial non-necrotizing granulomas




From an airway-centered to diffuse distribution

Lymphocytes > plasma cells


Interstitial non-necrotizing granulomas

Loose, poorly circumscribed interstitial collections of epithelioid histiocytes

admixed with variable numbers of multinucleated giant cells and

lymphocytes

Epithelioid histiocytes often present in the peribronchiolar interstitium



Plugs of pale staining, loose fibroblastic tissue filling

Distal bronchioles (bronchiolitis obliterans)

Alveolar ducts

Contiguous alveolar spaces

Foamy macrophages, fibrinous exudate, and neutrophils in alveolar

spaces secondary to bronchiolar obstruction

Microscopic features

Continued exposure can lead to fibrotic residua in the

histologic patterns of fibrotic NSIP or UIP

Absent lymphoid follicles with germinal centers, interstitial eosinophils and neutrophils, and vasculitis

Fig. 9




Fig. 10




Fig. 11




Fig. 12




Differential diagnosis

Organized into two groups:

Noninfectious interstitial lung disease, primarily sarcoidosis,

lymphoid interstitial pneumonia (LIP), NSIP, and UIP

Granulomatous infection

Sarcoidosis Morphology and distribution of the granulomas

Degree and distribution of the chronic interstitial

inflammation.

Sarcoidosis HP

Granulomas compact, well circumscribed,

sometimes hyalinized,

distributed in a lymphangitic pattern

along bronchovascular bundles, pleura, and interlobular septae

Loose, poorly circumscribed,

lack hyalinization,

confined to a peribronchiolardistribution

Chronic interstitial inflammation

accompanies the distribution of

granulomas

without significant extension into the adjacent parenchyma

greater degree of interstitial

inflammation

with more extensive

involvement of the surrounding parenchyma


- +

Fig. 13




Fig. 11




LIP

Densely cellular interstitial infiltrates of lymphocytes, plasma cells,

and histiocytes that markedly expand and distort alveolar walls.

LIP diffusely involves the lung parenchyma and lacks airway-

centered distribution

Lymphoid aggregates with reactive germinal centers

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Residual HP VS UIP VS Fibrotic NSIP

HP UIP NSIP

upper lobe lower lobe lower lobe

airway-centered

subpleural airway-centered

Granulomatous infections

Special stains for microorganisms in all biopsies with granulomas

Culture correlation

Hot tub lung

Controversially represents a hypersensitivity reaction or infection

Characterized by airway-centered non-necrotizing granulomas, organizing pneumonia, and chronic interstitial inflammation

Hot tub lung HP

Granulomas well-formed

distributed in both the interstitium and alveolar spaces

Loose, poorly circumscribed,

confined to a peribronchiolardistribution

Chronic interstitial inflammation

Tends to associated with the granulomas

More diffusely distributed in the lung parenchyma


++ +

An approach to biopsy diagnosis

Interpretation of biopsies in this setting is difficult since

granulomas occur in a wide array of disease processes

Multidisciplinary triangle of clinical, radiologic, and pathologic information


Active disease

Airway-centered chronic interstitial inflammation, poorly-formed

granulomas, and organizing pneumonia on biopsy

Widespread mosaic ground glass attenuation and centrilobular

nodules on chest CT

Rresidual disease

Presence of epithelioid histocytes and granulomas


Lung injury caused by infection > HP

Chest CT plays a critical role in identifying esp. mycobacterial infections

Treatment

Avoiding contact with the offending antigen is the cornerstone of

hypersensitivity pneumonitis treatment

Active disease typically resolves without sequelae

Oral corticosteroids serve to control symptoms but do not appear

to effect long-term outcome

The presence of fibrosis on histology or CT portents a poor

prognosis

Points in Histologic Evaluation of Hypersensitivity Pneumonitis

Interpreting biopsies with clinical and radiologic findings

Perform special stains for microorganisms and correlate with

cultures when granulomas are present on biopsy

Negative special stains do not exclude infection

hypersensitivity pneumonitis: radiology and pathology aspect

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histologic findings

constellation of findings

pathologic findings

middle lungs fibrosis

transbronchial biopsy

reproduction of symptoms

laboratory abnormalities

unilateral abnormalities