| yourself against this deadly enemy. | | | | need them, and old cells do not die when they |
| What Is Cancer? | | | | should. The extra cells form a mass of tissue |
| Cancer is a group of many related diseases that | | | | called a growth, or tumor. Not all tumors are |
| begin in cells, the body's basic building blocks. To | | | | cancerous; tumors can be benign or malignant. |
| understand cancer, it is helpful to know what | | | | Benign tumors are not cancer. They can often be |
| happens when normal cells become cancerous. | | | | removed and, in most cases, they do not come |
| Normally, cells grow and divide to produce more | | | | back. Cells in benign tumors do not spread to |
| cells as they are needed to keep the body | | | | other parts of the body. Most important, benign |
| healthy. Sometimes, this orderly process goes | | | | tumors are rarely a threat to life. |
| wrong. New cells form when the body does not | | | | |