Cancer is a group of diseases where cells divide uncontrollably and spread into surrounding tissues. Normally, cells grow and divide in a controlled way, but when cancer develops, this process goes wrong. Old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumors.
Cancer can start almost anywhere in the human body, which is made up of trillions of cells. It can invade nearby parts of the body and spread to other places. The spread happens when cancer cells get into the blood or lymph system.
There are many types of cancer. The names usually come from where the cancer starts. For example, lung cancer starts in the lung, and breast cancer starts in the breast. Spreading cancer is called metastasis.
Cancer treatment includes surgery, radiation, chemotherapy, and targeted therapy. The goal is to remove, kill, or control the cancer cells.