Tumors can be benign or malignant. Benign tumors are not cancer. They often can be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life.
Malignant tumors are cancer.
Cells in malignant tumors are abnormal and divide without control or order. These cancer cells can invade and destroy the tissue around them. This process, called metastasis, is how cancer spreads from the original tumor to form new tumors in other parts of the body. Cigarette smoking is the most significant cause of lung cancer and the leading cause of lung cancer death in both men and women. Smoking is also responsible for most cancers of the larynx, oral cavity, and esophagus.