Your body is made up of many different types of cells. Under normal conditions, cells grow, divide, become old, and die. Then, in most cases, they’re replaced by new cells. But sometimes cells mutate grow out of control, and form a mass, or tumor, instead of dying.
Tumors can be benign (noncancerous) or malignant (cancerous). Cancerous tumors can attack and kill your body’s tissues. They can also spread to other parts of the body, causing new tumors to form there. This process is called metastasis and it represents cancer that has advanced to a late stage.