What Is Cancer?
Cancer is a group of more than 100 different diseases. Cancer occurs when cells become abnormal and keep dividing and forming more cells without control or order.
Like all the other organs of the body, the lungs are made up of many types of cells. Normally, cells divide to produce more cells only when the body needs them. This orderly process helps keep us healthy.
If cells divide when new cells are not needed, a mass of tissue forms. This mass of excess tissue, called a growth or tumor, can be benign or malignant.
Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Most important, the cells in benign tumors do not invade other tissues and do not spread to other parts of the body. Benign tumors are rarely a threat to life.
Malignant tumors are cancer. They can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. This is how cancer spreads from the original tumor and forms new tumors in other parts of the body. The spread of cancer is called metastasis. Read more »