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Chapter 3: Occupational lung disease 133

alveoli and then thickened, cystic spaces (honeycomb Pathophysiology
lung). Two different syndromes result from inhalation:
Malignant mesothelioma: Thoracoscopic or open Simple pneumoconiosis in which there is deposition

lung biopsy may be needed to make the diagnosis. of coal dust within the lung. There are peribronchiolar
Macroscopically the lesion is thick, may be encapsu- depositsintheupperpartsofthelung,oftenassociated
lated, with interlobar fissures. The tumour may be with mild centri-acinar emphysema.
hard and white or glutinous due to the production Progressive massive fibrosis (PMF): The pathogenesis
of hyaluronic acid. Histological pattern is variable, it is not understood. Patients develop rheumatoid and
may be epithelioid, fibrous or mixed. Local invasion antinuclearfactorandthedamageisthoughttobedue
is extensive, 50% metastasise. to immune complexes.
Asbestos-related carcinoma of the bronchus: Asbesto-

sis and cigarette smoking act synergistically to cause Clinical features
afivefold increase in the risk of developing bronchial Simple pneumoconiosis is asymptomatic. Patients with
carcinoma, which is usually adenocarcinoma or squa- progressive massive fibrosis suffer from considerable ef-
mous cell carcinoma. fort dyspnoea, usually with a cough. The sputum may
be black.
Management
All patients with known asbestos exposure should be

Macroscopy/microscopy
advised to stop smoking. Routine surveillance with
Simplepneumoconiosisischaracterisedbyaccumula-
repeated sputum cytology and chest X-ray does not
tion of dust in macrophages at the centre of the acinus,
appear to lead to earlier diagnosis.
with associated emphysema.
Pleural plaques and asbestos bodies require no treat-

In progressive massive fibrosis there are nodules of
ment. Asbestosis is treated as for respiratory failure
>3cmin the upper lobes. Histologically the nodules
when this occurs.
can be divided into three types:
Mesothelioma treatment is largely palliative, resection

i Amorphous collection of acellular proteinaceous
may be attempted in early disease. Radiotherapy is in-
material, containing little collagen and abundant
effective and chemotherapy regimens are under eval-
carbon, which frequently cavitates and liquefies.
uation.
Seen where silica content is low.
Patients with bilateral diffuse pleural thickening, as-

ii Dense collagenous tissue and macrophages heavily
bestosis and (in those with an occupational history or
pigmented by carbon, seen where there is a high
other evidence of asbestos exposure) mesothelioma or
silica content in the coal dust.
carcinoma of the bronchus are entitled to industrial
iii Caplan’s syndrome seen where there is co-existent
compensation.
rheumatoid disease. Carbon-stained rheumatoid
nodules are seen.
Coal worker’s pneumoconiosis
Definition Complications
Pathology resulting from inhalation of coal dust and its Simple pneumoconiosis is divided into three stages by
associated impurities. chest X-ray appearance (see Table 3.20). Stage 1 does
not progress, 7% of patients with stage 2 and 30% of
Prevalence patients with stage 3 will go on to develop progressive
Twoper 1000 coal workers. massive fibrosis. PMF by definition is progressive, and
respiratory failure will eventually develop.
Aetiology
The disease is caused by dust particles approximately Investigations
2–5 µmin diameter that are retained in the small airways The diagnosis is made by chest X-ray in those who have
and alveoli of the lung. been exposed (see Table 3.20).