The risk of lung cancer relates to the duration of smoking. The sooner a smoker stops smoking, the sooner the risk will cease to increase. Today lung cancer is the leading cause of death from cancer in men and women. Cancer is a disease in which abnormal cells in some organs or tissue go out of control, growing and increasing in number. Normal cells reproduce themselves throughout life, but in an orderly and controlled manner.
Normal growth occurs, worn out tissues are replaced and wounds heal.
When cells grow out of control and form a mass, the mass is called a tumor. Other tumors not only enlarge locally but also have the potential to invade and destroy the normal tissue around them and to spread to distant parts of the body. Such tumors are called malignant tumors, or cancer. Because of the different manner in which tissue cells in the same organ system may respond to varying types of exposure to cancer producing agents, several different types of cancer may be found in any organ. This is well illustrated by the primary cancers affecting the lung, which are described below.