Conglomerate Mass (Progressive Massive Fibrosis)

Jeffrey P. Kanne, MD

DIFFERENTIAL DIAGNOSIS

Common

Sarcoidosis
Radiation-Induced Lung Disease

Less Common

Silicosis/Coal Worker’s Pneumoconiosis
Diffuse Alveolar Hemorrhage

Rare but Important

Lipoid Pneumonia
Pulmonary Talcosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Significant overlap of findings between sarcoidosis and silicosis and coal worker’s pneumoconiosis
Occupational and exposure history important
Knowledge of treatment plan useful for recognizing radiation-induced lung fibrosis
- Important for distinguishing radiation-induced lung disease from recurrent neoplasm

Helpful Clues for Common Diagnoses

Sarcoidosis
- Develops with progressive sarcoid-induced fibrosis
- Conglomerate fibrosis difficult to distinguish from silicosis or coal worker’s pneumoconiosis
  - Upper and mid lung zone predominant
  - Air bronchograms usually present
  - Associated traction bronchiectasis, architectural distortion, and volume loss
  - Punctate or coarse calcification frequently present
  - Perilymphatic nodules typically present bilaterally
- Paracicatricial emphysema common peripheral to conglomerate mass
  - Increases with progressive fibrosis
- Cavitation may occur from necrosis or infection
  - Mycobacterium species
- Mediastinal and bilateral hilar lymphadenopathy often present
  - May be calcified (solid or “egg shell”)
- Honeycombing less common than with other end-stage lung diseases
  - Cysts usually larger
  - Basal sparing typical
Radiation-Induced Lung Disease
- Most commonly result of radiation for lung carcinoma
- Less commonly for mediastinal lymphoma, esophageal carcinoma, or breast carcinoma
- Radiation fibrosis
  - Typically occurs 6-12 months after completion of radiation therapy
  - Occurs within radiation field and can cross anatomic boundaries, such as pulmonary fissures
  - Straight lateral and medial margins with conventional therapy
  - May begin as small consolidative or ground-glass attenuation lung nodules
  - Nodules coalesce over time to form larger areas of fibrosis
  - Newer 3D radiation therapy techniques can result in lung abnormalities away from primary disease
  - Should stabilize within 2 years following therapy

Helpful Clues for Less Common Diagnoses

Silicosis/Coal Worker’s Pneumoconiosis
- Exposure to coal dust or free silica
  - Coal miners
  - Quarry workers
  - Sand blasters
  - Foundry workers
  - Ceramics workers
  - Concrete cutters
- Typically develops after 20 years of exposure
  - Can develop < 10 years with exposure to very high concentrations of dust
  - Progresses despite cessation of exposure
- Silicosis and coal worker’s pneumoconiosis indistinguishable radiographically
- Large opacities > 1-2 cm
- Begins in periphery of lung
  - Round or oval nodule or mass
  - Well-defined lateral margin paralleling chest wall
  - Posterior location on lateral radiograph or CT
  - Unilateral or asymmetric in early stages
  - Becomes symmetric with progressive disease
- Difficult to distinguish from sarcoidosis
  - Develops in upper lobes
  - Air bronchograms less common than with sarcoidosis
  - Associated with bronchial distortion and upper lobe volume loss
  - Small perilymphatic nodules usually present
- Cavitation may occur from necrosis or infection, especially when > 5 cm
  - Predisposed to Mycobacterium tuberculosis infection
- Punctate calcifications common in conglomerate masses
- Mediastinal and hilar lymphadenopathy in up to 40%
  - Calcification in ˜ 50% (diffuse, central, eccentric, and peripheral “egg shell”)
- Paracicatricial emphysema common peripheral to conglomerate mass
- Increased risk of lung carcinoma independent of cigarette smoking
- Increased risk of developing connective tissue disease, especially systemic sclerosis
Diffuse Alveolar Hemorrhage
- Very rare cause of conglomerate mass
- Occurs with recurrent alveolar hemorrhage
  - Subsequent hemosiderosis and fibrosis
- Conglomerate mass with high attenuation

Helpful Clues for Rare Diagnoses

Lipoid Pneumonia
- Typically result of recurrent lipid aspiration
  - Most patients asymptomatic
  - Mineral oil ingestion most common
  - Occupational exposure to oil mist less frequent
- Conglomerate mass with diffuse low attenuation
- Usually gravitationally dependent (posterior lower lobes)
- Cavitation uncommon
  - Usually from superinfection with nontuberculous mycobacteria
Pulmonary Talcosis
- Frequently results from chronic intravenous drug abuse
  - Granulomatous vasculitis from foreign body giant cell reaction to contaminants (talc) in drugs
  - Patients often initially asymptomatic
  - May progress to respiratory insufficiency and pulmonary hypertension
- Early disease
  - Small nodules
  - Hyperinflation and emphysema (panlobular or panacinar)
- Conglomerate masses develop with progressive disease
  - Similar to those of silicosis and coal worker’s pneumoconiosis
  - May have diffuse or punctate calcification