Primary lung cancer in South Wales coal-workers with pneumoconiosis.

Coal-workers in the southern part of Wales are particularly prone to pulmonary disease due to the inhalation of coal dust. In some men discrete foci of dust are scattered more or less uniformly throughout both lungs. This is called simple pneumoconiosis. In others there occur also one or more large localized masses of dust and dense fibrous tissue (Fig. 1). This manifestation is referred to as massive pneumoconiosis or progressive massive fibrosis. The literature contains many references to the coexistence of classical silicosis with primary lung cancer, but there are few accounts of coal-worker's pneumoconiosis with coexistent tumours. In a recent statistical study Kennaway and Kennaway (1953) have shown that primary cancer of the lung is less common in coal-workers than in the general male population. Their figures also show that in the South-Western Division of the British coalfields, where the incidence of pneumoconiosis is high, the incidence of lung tumour is low relative to that in other coalfields. In some other British coalfields where the pneumoconiosis incidence is low the tumour incidence is, for coal-workers, relatively high. The object of the present inquiry was to obtain evidence regarding the relationship, if any, of pneumoconiosis to lung cancer in South Wales coal-workers. The material was obtained during the six years 1947 to 1952 during which necropsies were made, in this department, on 1,827 coal-workers. During the same period post-mortem examinations were made of 1,531 South Wales males over the age of 21 not concerned with coal-mining. The pathological examinations of the miners were made on the instruction of coroners who had been told by the relatives that they considered death was due wholly or partly to dust disease. The symptoms of dust disease are well known to the mining community, and requests for necropsy are likely to be made by the relatives of men who have had chronic dyspnoea. This is shown by the high incidence of chronic lesions of the lung or cardiovascular system in this series. In many of the cases pneumoconiosis of varying degrees had been detected radiologically during life, and compensation had been paid. It was considered that useful information might be obtained by studying the material as follows: (1) Observation of the site of the cancer in relation to the site of the massive fibrosis in those in whom the two lesions coexisted; (2) comparing the cancer cases in the miners and non-miners in respect of the histological types of the tumours, the spread of metastases, and the age distributions at death; (3) by studying the incidence of cancer in relation to the severity of the dust lesion; (4) by comparing the cancer incidence in the miners with that found at necropsy in non-miners. At necropsy one of each pair of lungs was distended by formol-sodium-acetate solution with a view to the preparation of a large section by the technique of Gough and Wentworth (1949). The other lung was cut at the time of the necropsy and after naked-eye examination pieces were excised for microscopic study.