A cancerous cell develops when it ceases to respond to growth-inhibiting signals and gains the ability to multiply uncontrollably. If the cells divide when new ones are not needed, they form a mass of excess tissue called a tumor . This tumor, in turn, can damage healthy tissue in its area. The cancerous cells from this tumor also can break away and travel through the blood or the lymphatic system to form new tumors in other parts of the body. The spreading of the cancer in this fashion is called metastasia .
Types There are numerous forms of cancer that affect the human body.
About 1,208,000 new cancer cases will be diagnosed in 1995. Of those diagnosed, about 538,000 will die of cancer. Some of the more common forms of cancer are listed below. Prostate-an estimated 200,000 new cases in 1994 Cancer statistics from the American Cancer Society Causes Cancers have many different causes and sources. One of these sources is a group of chemicals called carcinogens .