What is Cancer?
The term cancer covers more than a hundred diseases that share one trait: In all of the diseases, cells grow out of control and destroy healthy tissues. Cancer tissue, growing without limits, competes with normal tissue for nutrients, eventually killing normal cells by nutritional deprivation.
Cancerous tissue can also cause secondary effects, in which the expanding malignant growth puts pressure on surrounding tissue or organs or the cancer cells metastasize and invade other organs. The spread of cancer is called metastasis. It is this ability for malignant tumors to spread to other vital organs, and disturb their functioning, that makes cancer dangerous. A few cancers, such as blood cancers (leukemia), do not form a tumor.
Cancer is NOT contagious. Cancer is the second leading cause of death in the United States.