What Is Cancer? Explanations about what cancer is, how cancer cells differ from normal cells, and genetic changes that cause cancer to grow and spread.

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A dividing breast cancer cell.

Credit: National Cancer Institute / Univ. of Pittsburgh Cancer Institute

A Collection of Related Diseases

Cancer is the name given to a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues.

Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.

from Cancer Information - What Is Cancer? Explanations about what cancer is, how cancer cells differ from normal cells, and genetic changes that cause cancer to grow and spread.