Glossary Term:





a group of diseases which cause cells in the body to change and grow out of control. Most types of cancer cells form a lump or mass called a tumor. (Not all tumors are cancer. A tumor that is not cancer is called benign, while a cancerous tumor is called malignant.) A cancerous tumor can invade and destroy healthy tissue. Cells from the cancer can break away and travel to other parts of the body. There they can continue to grow. This spreading process is called metastasis. When cancer spreads, it is still named after the part of the body where it started. For example, if colon cancer spreads to the liver, it is still colon cancer, not liver cancer.

Benign tumors do not grow and spread the way cancer does. They are usually not a threat to life. Note that some types of cancer, such as blood cancers, do not form tumors. They can still threaten life by crowding out normal cells. See also benign, malignant, metastasis, tumor.