Picture of Lung Cancer
Lung cancer is an invasive tumor of the lungs that arises due to damage to DNA. The body normally keeps cell growth and death under tight control. In the case of cancer, the system that controls and monitors cell growth malfunctions, allowing cancer cells to form and grow. Lung cancer often metastasizes, or spreads, very early in the disease process. That makes lung cancer particularly life-threatening and difficult to treat. The most common sites where lung cancer spreads include the brain, bones, liver, and adrenal glands.
Lung cancer may form in any part of the lung, but the vast majority of lung cancers (90% to 95%) occur in epithelial cells. These cells line the bronchioles and bronchi, branches of the airways. Lung cancer is responsible for more deaths in men and women worldwide than any other malignancy. Cigarette smoking and tobacco use contribute to approximately 90% of lung cancers. Lung cancer risk increases as the number of cigarettes smoked over a lifetime increases. The longer someone has smoked, the greater his or her risk of lung cancer.
Text Reference: American Cancer Society: "Lung Cancer"