How do cancerous tumors develop?
Cells in the body normally divide, or reproduce, only when new cells are needed. Sometimes, cells in a part of the body grow and divide out of control, which creates a mass of tissue called a tumor. If the cells that are growing out of control are more normal cells, the tumor is called benign, or non-cancerous. If, however, the cells that are growing out of control are abnormal, don't function like the body's normal cells, and begin to invade other tissue, the tumor is called malignant, or cancerous.
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