Cancer causes a total of 7.6 million deaths per year, or approximately 13% of deaths worldwide. Lung cancer being the most common type, it is responsible for 1.37 million of these deaths. But what are the main factors causing this type of cancer and what can be done to prevent the increasing number of deaths? Lung cancer can be defined as uncontrolled growth of abnormal cells in one or both lungs of an organism. These abnormal cells divide and multiply to create unhealthy tissue or tumors inside the lungs. These tumors interfere with the lungs' ability to supply oxygen to the body. Although lung cancer can start inside the lungs, it can also originate in other parts of the body. When cancer starts inside the lungs, it is called primary lung cancer, when cancer starts in other parts of the body and spreads to the lungs, it is called secondary lung cancer. These two different origins of cancer make treatments and symptoms very similar, although primary lung cancer is the leading cause of lung cancer death worldwide. Lung cancer can be further divided into types and stages of development to determine the severity of the disease. , there are several types of lung cancer and four stages of development. The two main types of lung cancer include non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). According to the American Cancer Association, 85% of lung cancers are non-small cell lung cancers, while small cell lung cancer is less common in the remaining 15%. However, there are several subtypes of NSCLC. The most common include: squamous cell (squamous cell) carcinoma, adenocarcinoma, and large cell carcinoma. The subtypes of NSCLC...... middle of paper ......cer Society. Np, and Web. April 25, 2014. “Lung cancer.” Basics of lung cancer. Mayo Clinic, nd Web. April 27, 2014. “Lung Cancer Fact Sheet – American Lung Association.” American Lung Association. American Lung Association, nd Web. April 26, 2014. “Lung Cancer.” Lung cancer. National Institute of Health, nd Web. April 26, 2014. “Lung cancer: treatment and care.” WebMD. WebMD and Web. April 27, 2014. “Lymph node.” Wikipedia. Wikimedia Foundation, April 27, 2014. Web. April 27, 2014. “Radon and Cancer – National Cancer Institute. » Radon and cancer - National Cancer Institute. National Cancer Institute, nd Web. April 27, 2014. “Smoking.” - National Cancer Institute. Np, and Web. April 27, 2014. “What are we doing to protect people from the dangers of smoking? » What are we doing to protect people from the dangers of smoking? American Cancer Society, nd Web. April 27. 2014.