The most common site where lung cancer develops is inside a bronchus, called bronchogenic carcinoma. According to the U.S. Centers for Disease Control and Prevention, in 2006, 106,374 men and 90,080 women were diagnosed with lung cancer, and more people die from lung cancer than any other cancers. Cancerous growths can also occur in other tissues inside the chest, including the pleural membranes that surround the lungs. Three types of lung cancer that can develop inside a bronchus causes serious symptoms because tumors can block the passage of air into the lungs.
Squamous Cell Carcinoma
Squamous cell carcinoma accounts for about 30 to 40 percent of bronchogenic carcinomas. According to the U.S. Centers for Disease Control and Prevention, or CDC, it is strongly linked to tobacco smoking and occurs mainly in the large bronchi, where it can block and interfere with air flow. These tumors grow slowly, and generally respond well to radiation therapy at first, but not to chemotherapy. The CDC also states that life expectancy in America has somewhat improved in recent years, as tobacco smoking decreases.
Small-cell Carcinoma
Small-cell carcinoma accounts for 20 to 30 percent of bronchogenic carcinomas, with tobacco smoking being the probable cause. According to the National Comprehensive Cancer Network, the cancer spreads rapidly and extensively throughout the body. If treated early, it responds fairly well to chemotherapy, which may be combined with radiation therapy. Small-cell carcinoma cancer cells are small, oval-shaped cells when examined under a microscope, hence the name, small-cell carcinoma.
Non Small-cell Carcinoma
Non small-cell carcinoma accounts for 10 to 20 percent of bronchogenic carcinomas and is also strongly linked to tobacco smoking. According to the CDC, non small-cell carcinoma, unlike small-cell carcinoma, spreads inside the lungs then to other structures in the chest cavity and eventually throughout the body. Chemotherapy and radiation therapy are usually ineffective, depending on the stage of the cancer at diagnosis.
Adenocarcinoma
Adenocarcinoma accounts for 25 percent of bronchogenic carcinomas and the link to tobacco use is less clear. Adenocarcinoma of a bronchus often spreads outside the chest cavity, principally to the brain and spine. This cancer affects the lung's air sacs, as well as the smallest airways and can spread to larger areas of the lung. These carcinomas do not respond well to chemotherapy, and radiation therapy is only somewhat effective, even when found in early stages of the disease.
