Lung cancer is one of the more common cancers in the United States. According to the National Cancer Institute, more than 219,000 cases of lung cancer were diagnosed in 2009. Not all cases of lung cancer are the same and catching the cancer early in the disease's process can increase the likelihood of survival.
Lung Cell Cycle
Cells in the lung grow and divide under fairly strict control. Lung cell reproduction is governed by a series of chemical signals that are made both within and outside of the cell to make sure that the cells only divide when necessary. Consequently, in any given tissue sample within the lungs, the majority of the cells will be at rest instead of actively dividing. Chemical signals also are used to make old and damaged cells die.
Mutations
Lung cancer is the result of genetic mutations that disrupt the normal control of cell reproduction and death, according to the National Cancer Institute. The genetic mutations cause the proteins that govern the cell cycle to malfunction. Often these genetic changes are a result of inhalation of tobacco smoke and exposure to other DNA-damaging substances. As a result, old and damaged cells do not die and new cells form when and where they are no longer needed. This leads to the formation of a tumor.
Lung Cancer Types
Different kinds of lung cancer progress differently within the body. The most common kind of lung cancer, according to the Patient Education Institute, is non-small cell lung cancer. This kind of lung cancer grows rather slowly and does not spread as easily to other parts of the body. Small-cell lung cancer, on the other hand, grows very quickly and is more likely to spread to other parts of the body.
Early-Stage Lung Cancer
Lung cancer is broken up into four different stages, according to the American Cancer Society. During the lung cancer process, the cancer will begin at the earliest stage but may progress into more advanced stages over time. In the earliest sage of lung cancer, called stage I, the tumor is relatively small (less than 3 cm in diameter) and has not spread to any of the surrounding lung tissues. Stage II lung cancer can be between 3 and 7 cm in diameter and may have grown into some of the membranes that surround the lung, also known as the pleura.
Late-Stage Lung Cancer
As lung cancer progresses, it gets bigger and begins to invade other tissues throughout the body. Stage III lung cancer is any tumor that is bigger than 7 cm across or that has grown into the diaphragm, the chest wall or has spread to the area in between the lungs. Stage IV cancer, which is the final stage of lung cancer, describes cancer that has spread to other areas throughout the body, including the backbone, the esophagus and windpipe, or the area around the heart.
