Lung cancer pathology in smokers, ex-smokers and never smokers.

The histologic distribution of lung cancer is markedly different in smokers and non-smokers. It is not known whether the histology among former smokers varies according to the number of years since quitting. Using data from a large case-control study of lung cancer, we found that for both men and women, the proportion of adenocarcinomas increased with the number of years since quitting smoking. Among long-term quitters (> 25 years), the proportion of adenocarcinomas was similar to that in never smokers. These findings have implications for studies of environmental tobacco smoke and lung cancer.