in smokers and non smokers
1 Small cell lung cancer. 2  Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer. 3  Non-small cell lung cancer. 4  Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Medical Editor: Jay W. Marks, MD. While cigarette smoking is an undisputed cause of lung cancer, not all cases of lung cancer occur in smokers or former smokers. Each year, over 170,000 Americans develop lung cancer, and approximately ten per cent of lung cancers, or 17,000 cases, occur in non-smokers. Lung cancers in non-smokers are often different in some ways from those that occur in smokers. They tend to occur at younger ages. Lung cancers in non-smokers often have certain gene changes that are different from those in tumors from smokers. In some cases, these changes can be used to guide treatment. 1 Numerous studies have shown that lung cancer is more likely to occur in both smoking and non-smoking relatives of those who have had lung cancer than in the general population. 2  Air pollution from vehicles, industry, and power plants, can raise the likelihood of developing lung cancer in exposed individuals. 1 Non-smokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with other non-smokers. 2  Each year, up to 3,000 lung cancer deaths are estimated to occur in the U.S. that are attributable to passive smoking. About 15% of all lung cancer cases are SCLC. Small cell lung cancer is slightly more common in men than women. Almost all cases of SCLC are due to cigarette smoking. SCLC is rare in people who have never smoked. SCLC is the most aggressive form of lung cancer. Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. Why Does Lung Cancer Occur in Non-Smokers. While cigarette smoking is an undisputed cause of lung cancer, not all cases of lung cancer occur in smokers or former smokers. Gani Fawehinmi, who is reportedly a non-smoker, died of lung cancer on September 5, 2009. Bronchioles and alveoli. Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure
http://www.mayoclinic.org/diseases-conditions/lung-cancer/basics/causes/CON-20025531 http://www.medicinenet.com/script/main/art.asp?articlekey=53012 http://www.cancer.org/cancer/lungcancer-non-smallcell/detailedguide/non-small-cell-lung-cancer-what-causes http://www.medicinenet.com/script/main/art.asp?articlekey=53012 http://www.medicinenet.com/script/main/art.asp?articlekey=53012 https://www.nlm.nih.gov/medlineplus/ency/article/000122.htm http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004529/ http://lungcancercircleofhope.org/?p=294 http://www.mayoclinic.org/diseases-conditions/lung-cancer/basics/causes/CON-20025531
where does lung cancer occur