Normally the cells that make up the body grow, divide, and replace themselves in an orderly manner. This process keeps the body in repair. Sometimes, however, cells lose their ability to limit and direct their growth, and they divide rapidly without any order. These cells grow into masses of tissue known as tumors.
Tumors can be either benign or malignant.
Benign tumors are not cancer. They usually grow slowly, and generally do not spread to other parts of the body. Benign tumors can usually be removed surgically without any further problems. Malignant tumors are cancer. The most common methods for cancer to spread are through the lymphatics to regional lymph nodes or through the bloodstream to distant organs.