When removed, benign tumors usually don’t grow back, whereas cancerous tumors sometimes do. Many cancers form solid tumors, but cancers of the blood, such as leukemias, generally do not.īenign tumors do not spread into, or invade, nearby tissues. Cancerous tumors may also be called malignant tumors. Tumors can be cancerous or not cancerous ( benign).Ĭancerous tumors spread into, or invade, nearby tissues and can travel to distant places in the body to form new tumors (a process called metastasis). These cells may form tumors, which are lumps of tissue.

Sometimes this orderly process breaks down, and abnormal or damaged cells grow and multiply when they shouldn’t. When cells grow old or become damaged, they die, and new cells take their place.

Normally, human cells grow and multiply (through a process called cell division) to form new cells as the body needs them. of Pittsburgh Cancer Institute The Definition of CancerĬancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body.Ĭancer can start almost anywhere in the human body, which is made up of trillions of cells. Credit: National Cancer Institute / Univ.

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