Lung cancer is the number one cause of cancer deaths in both men and women in the U.S. and worldwide. Cigarette smoking is the principal risk factor for development of lung cancer. Second hand exposure to tobacco smoke also can cause lung cancer.

The two types of lung cancer, which grow and spread differently, are the small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). The stage of lung cancer refers to the extent to which the cancer has spread in the body.

Cancer of the lung, like all cancers, results from an abnormality in the body’s basic unit of life, the cell. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when new cells are needed. Disruption of this system of checks and balances on cell growth results in an uncontrolled division and proliferation of cells that eventually forms a mass know as a tumor.

Tumors can be benign or malignant. When we speak of cancer we are referring to those tumors that are malignant. Benign tumors usually can be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, grow aggressively and invade other tissues of the body, allowing entry of tumor cells into the bloodstream or lymphatic system and then to other sites in the body.