Lung cancer in a defined geographical area: history and histological types.

Lung cancer was diagnosed in 446 patients during four years in a population living in a defined geographical area in northern Finland. The series comprised 420 men and 26 women, with a male/female ratio of 16.6:1. The diagnosis was confirmed histologically or cytologically in 431 cases (97%). Epidermoid carcinoma was the most common histological type of tumour in the men, followed by small cell anaplastic and adenocarcinoma, whereas in the women all these types were of equal frequency. Almost all the men, but only about half of the women, were smokers or ex-smokers. The amount smoked daily had no correlation with the histological type of cancer, whereas those patients who had started smoking early had relatively more Kreyberg group I tumours (epidermoid, small cell, and large cell carcinoma) than those who had started smoking late. Cancer was usually detected on the basis of symptoms, but 17% emerged from mass radiography or some health examination, and 12% from examinations for another disease. Fifteen per cent of the patients had no symptoms at the time of diagnosis, this being more common among the patients with epidermoid or adenocarcinoma than among those with anaplastic forms.