The body is made up of many types of cells. Normally, cells grow and divide to produce more cells only when the body needs them. This orderly process helps keep the body healthy. Sometimes cells keep dividing when new cells are not needed. These extra cells may form a mass of tissue, called a growth or tumor.
Cancer can begin in any organ or tissue of the body.
The original tumor is called the primary cancer or primary tumor and is usually named for the part of the body in which it begins. Metastatic cancer is cancer that has spread. Cancer cells can break away from a primary tumor and travel through the bloodstream or lymphatic system to other parts of the body. The cancer cells may build up in lymph nodes near the primary tumor, and they may travel to distant parts of the body. The spread of cancer cells is called metastasis.