Lung cancer is currently the leading cause of cancer related deaths in both men and women in the United States. Lung caners are usually one of the two major categories, small cell lung cancer, SCLC which consists of about 15% of lung cancer cases, and non small cell lung cancer, NSCLC, which consists of about 85% of all lung cancer cases. I will be concentrating on non small cell lung cancer. Non small cell lung cancer is defined as any type of epithelial lung cancer that is other than small cell lung carcinoma. Non small cell lung cancer usually grows and spreads more slowly than small cell lung cancer.

Non small cell lung cancer is divided into three main categories: squamous cell (epidermoid) carcinoma, adenocarcinoma, and large cell, undifferentiated, carcinoma.

About twenty 25-30 % of all lung cancers are squamous cell carcinomas. Squamous cell cancers start in early versions of squamous cells. Squamous cells line the inside of the airways in the lungs. Squamous cell carcinomas are often linked to a history of smoking and tend to be found in the middle of the lungs, near a bronchus.

About 40% of lung cancers are adenocarcinomas. Adenocarcinomas start in the cells that would normally secrete substances such as mucus. Adenocarcinoma most often occur to people who currently smoke, may have smoked in the past, but adenocarcinomas are also the most common lung cancer that non-smokers acquire. Adenocarcinoma occur more common to women than to men. Adenocarcinomas also have a higher frequency of occurrence in young people than other lung cancers. Adenocarcinomas are usually found in the outer region of the lung, and are more likely to be found before it has spread outside of the lung due to its slow rate of growth and metastasis. There are seven distinct stages of lung cancer development: occult (hidden) stage, stage 0 (carconoma in situ), stage I, stage II, stage IIIA, stage IIIB. And stage IV, which depend on the size, malignancy and the location of the tumor.

Even though several risk factors for non small cell lung cancer have been identified, it does not mean that know we know the exact mechanism that is involved in transforming these normal cells into cancerous cells and new risk factors for non small cell lung cancer are constantly being discovered. Some of the known risk factors for NCSLC include: exposure to tobacco smoke, radon, asbestos, arsenic, radioactive substances, diesel exhaust, air pollution; inhaled chemicals or minerals such as arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, chromium compounds, coal products, mustard gas, and chloromethyl ethers. radiation treatments to the lungs, and a parsonal or family history or lung cancer. Tobacco smoking is widely considered to be the leading risk factor for lung cancer. Studies suggest that 80% of lung cancer cases are due to tobacco smoking. Studies also suggest that a person who smokes is 13 times as likely to develop lung cancer as apposed to a person who has never smoked. Studies have also shown that there is a direct correlation between the time the person has been smoking and the risk of developing lung cancer as well as a correlation between the risk of developing lung cancer and the amount of cigarettes smoked; the longer and the more cigarettes a person smokes the higher the likelihood is of the person developing lung cancer. Once a person stops their risk for developing lung cancer decreases the longer they stop smoking.

Studies have also shown that some individuals may have inherited a genetic predisposition for acquiring non small cell lung cancer. A study published in the journal Nature and one published in the journal Nature Genetics have both shown that a genetic alteration of the genes on the fifteenth chromosome are involved in the body's response to nicotine, and this is the pathway that this form of cancer is thought to target.

Studies have also shown that only a family history of lung cancer, not that of other kinds of cancer, is linked to inherited risk of lung cancer. Several genes such as Dmp1 have also been to have been identified to be associated with lung cancer; however much more research is needed to determine weather genetic mutations in those specific genes can be passed down or inherited from the parents to their offspring.