These cells reproduce by dividing. Through this process the body grows and repairs itself. Sometimes, a cell begins dividing abnormally and tumors form. Tumors may be benign or malignant. This is called metastasis.
Cancers grow at different speeds.
Some cancers are easily cured, others are more difficult to treat. This depends largely on the place in the body where the cancer cells grow, how large the tumor is when it is first found, and if it has spread. Generally, each type of cancer has its own symptoms, outlook for cure, and methods of treatment. No one knows for sure why a normal cell becomes a cancer cell. Many causes of cancer have been identified.