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Progressive Massive Fibrosis (PMF) is the advanced stage of pneumoconiosis (especially coal workers’ pneumoconiosis and silicosis) characterized by the coalescence of small nodules into large fibrotic masses (>1–2 cm), leading to severe distortion of lung architecture and progressive respiratory impairment.

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Etiopathogenesis

Inhaled inorganic dust (coal, silica) → deposition in alveoli → engulfed by macrophages.
Chronic inflammation with fibroblast activation → nodular fibrosis.
Over time, multiple small nodules coalesce, forming large fibrotic masses (>2 cm).
Masses may undergo cavitation (ischemic necrosis, secondary TB, rheumatoid nodules in Caplan’s syndrome).
Progressive contraction of fibrotic tissue → distortion of bronchi, vessels, and emphysematous change in surrounding lung.

Clinical Features

Symptoms: chronic cough, progressive dyspnea, reduced exercise tolerance.
Complications:
- Chronic respiratory failure.
- Pulmonary hypertension → cor pulmonale.
- Increased risk of TB (esp. in silicosis).
- Increased susceptibility to infections.
- May coexist with rheumatoid arthritis (Caplan’s syndrome).

Radiology

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PMF = large fibrotic masses (>2 cm), typically upper lobes, arising from coalescence of nodules in pneumoconiosis. Associated with cavitation, TB, emphysema, and cor pulmonale.

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Modality	Imaging features
XR	• Large opacities (>1 cm, often several cm) in upper and mid lung zones.
• Bilateral, irregular or rounded masses.
• May migrate towards the hilum with progressive fibrosis.
• Background of small nodules typical of simple pneumoconiosis.
• Possible cavitation (ischemic necrosis or TB).
• Associated compensatory emphysema in adjacent lung.
CT	• Massive, irregular fibrotic lesions (usually ≥2 cm) with retraction of surrounding lung.
• Predominantly in upper lobes.
• Confluent nodules, paracicatricial emphysema.
• Distorted bronchovascular bundles.
• Calcified mediastinal or hilar nodes (classic “eggshell” in silicosis).
• Cavitation: secondary TB or necrosis.
• Differentiation from malignancy may be difficult—look for stability, distribution, and background nodularity.

![Silicosis progressing to PMF in a 74-year-old stone mason. (a) CT shows small nodules in peribronchial and subpleural distribution. Confluent subpleural nodules form a pseudoplaque (arrow) in the left upper lobe. (b) Four years later, conglomerate masses have developed with architectural distortion and traction bronchiectasis in the upper lobes.

Batra K, Aziz MU, Adams TN, Godwin JD. Imaging Of Occupational Lung Diseases. Seminars in Roentgenology. 2018;54(1):44-58. doi:https://doi.org/10.1053/j.ro.2018.12.005](attachment:fa02adc7-f06a-43c8-9728-1d4e31bd4038:image.png)

Silicosis progressing to PMF in a 74-year-old stone mason. (a) CT shows small nodules in peribronchial and subpleural distribution. Confluent subpleural nodules form a pseudoplaque (arrow) in the left upper lobe. (b) Four years later, conglomerate masses have developed with architectural distortion and traction bronchiectasis in the upper lobes.

Batra K, Aziz MU, Adams TN, Godwin JD. Imaging Of Occupational Lung Diseases. Seminars in Roentgenology. 2018;54(1):44-58. doi:https://doi.org/10.1053/j.ro.2018.12.005

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Etiopathogenesis

Clinical Features

Radiology

Differentials