Tumours in Iceland. 7. Malignant epithelial tumours of the lung. A histological classification, epidemiological considerations and relation to smoking.

All malignant epithelial tumours of the lung submitted for a histological diagnosis in Iceland during the 20 years, 1955-1974, and available for review, were typed histologically according to the World Health Organization Classification originally published in 1967 and later revised and republished in 1981. The series includes 355 tumours, 217 from males and 138 from females, and 78 per cent of all registered malignant tumours of the lung. Among males the incidence of squamous cell carcinoma and small cell carcinoma was about equal and adenocarcinoma was in the third place. Among females the incidence of adenocarcinoma was the highest and that of small cell carcinoma in second place, other types being much less frequent. During the period there was a rise in the incidence of all the major histological types in both sexes and the greatest rise was in adenocarcinoma, where the incidence doubled in males and tripled in females. Among European nations the incidence of lung carcinoma is the lowest for Icelandic males and the highest for Icelandic females. There is a close correlation between the sale of cigarettes and the incidence of lung carcinoma in Iceland. Among those lung carcinoma patients with known smoking histories, all with small cell carcinoma, almost all with squamous cell carcinoma and four out of five with adenocarcinoma were smokers.