An epidemiological study of lung cancer: history and histological types in a general population in northern Finland.

A prospective epidemiological study was conducted to assess the incidence, diagnosis, histology and surgical treatment of lung cancer in northern Finland. The results were compared with those obtained in a similar survey 20 yrs earlier. Most of the patients with a suspected lung tumour were interviewed (72%) and the information was combined with that obtained from the national cancer registry. All pathological specimens were re-evaluated by a pathologist. A total of 602 new lung cancer cases (85% male, 15% female) were diagnosed during the years 1990-1992, the annual incidence per 100,000 being 63 for males and 9.5 for females. The number not reported to the Finnish Cancer Registry was low (<1%). Lung cancer was confirmed histologically in 381 cases (63%) and in addition cytologically in 135 cases (23%). Squamous cell carcinoma was the most common histological type (40%), the proportion of adenocarcinoma being 26%, small cell carcinoma 24% and large cell carcinoma 4%. The incidence of lung cancer had decreased significantly among males (from 87 to 63 per 100,000) compared with 20 yrs earlier but had increased among females (from 4.1 to 9.5), chiefly on account of adenocarcinoma. The findings of this prospective study show an increase in the incidence of lung adenocarcinoma among females, a histological type which is less closely related to smoking than the other cancers. This suggests that other risk factors may play an increasing role in the aetiology of lung cancer.