Follicular Bronchiolitis

Jud W. Gurney, MD, FACR

Key Facts

Terminology

Follicular bronchiolitis to nodular lymphoid hyperplasia (pseudolymphoma), LIP, and lymphoma

Imaging Findings

Centrilobular nodules, faint
Diffuse or lower lung zones
Nodules < 3 mm in diameter
Follicular bronchiolitis centered on airways (leads to centrilobular nodules), LIP more diffuse
Unusual: Cysts, mosaic air-trapping

Top Differential Diagnoses

Pathology

BALT extends from nodal clusters in airway bifurcations to lymphocyte clusters at proximity of lymphatics in terminal bronchioles
Idiopathic (but rare, most cases associated with other conditions)
Autoimmune: Sjögren syndrome (25% develop LIP), rheumatoid arthritis
Viral infection: HIV
Immunodeficiency: Common variable immunodeficiency, IgA deficiency
Inhalation: Cigarette smoke, polyethylene-flock, hypersensitivity pneumonitis

Clinical Issues

Micropathology shows peribronchiolar

germinal centers

in a patient with follicular bronchiolitis.

Axial HRCT shows faint centrilobular nodules

and tree-in-bud opacities

. Follicular bronchiolitis was the diagnosis.

TERMINOLOGY

Abbreviations and Synonyms

Pulmonary lymphoid hyperplasia, lymphocytic interstitial pneumonia (LIP), lymphoid interstitial pneumonia
Diffuse hyperplasia of bronchus-associated lymphoid tissue (BALT), mucosa-associated lymphoid tissue (MALT)

Definitions

Spectrum of lymphoid disorders
- Follicular bronchiolitis to nodular lymphoid hyperplasia (pseudolymphoma), LIP, and lymphoma
Nonneoplastic lymphoproliferation must be differentiated from lymphoma by immunologic stains
- Monoclonal cell lines in lymphoma, polyclonal in nonneoplastic lymphoproliferative disorders

IMAGING FINDINGS

General Features

Best diagnostic clue: Centrilobular nodules, faint
Patient position/location: Diffuse or lower lung zones
Size: Nodules < 3 mm in diameter
Morphology: Follicular bronchiolitis centered on airways (leads to centrilobular nodules), LIP more diffuse

CT Findings

Nodules (100%)
- Distribution within the lung
  - Diffuse (66%)
  - Lower lung zones (25%)
  - Axial plane: Peripheral lung (70%), central lung (0%), random (30%)
- Distribution within secondary pulmonary lobule
  - Centrilobular (100%)
  - Peribronchial (40%)
  - Subpleural (25%)
- Size
  - < 3 mm diameter (100%)
  - 3-10 mm diameter (40%)
  - > 10 mm diameter (< 10%)
Ground-glass opacities (75%)
- Nonsegmental diffuse patchy opacities
- Always associated with nodules
  - As profusion of nodules increases, more likely to have ground-glass opacities
Tree-in-bud opacities (70%)
Less common
- Bronchial dilatation (33%)
- Bronchial wall thickening (33%)
- Emphysema (33%)
- Architectural distortion (25%)
- Septal thickening (10%)
Mediastinal or hilar lymphadenopathy (50%)
- Mildly enlarged, 1-2 nodal groups (will not be large enough to be detected radiographically)
Unusual
- Cysts
- Mosaic air-trapping
Absent
- No honeycombing
- No pleural effusions
- No “crazy-paving”
Evolution
- Relatively stable over time, small series followed mean 4 years
  
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