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Cancer cells grow and
divide out of control
Section 9.4
Tumors and Cancer
• Out-of-control cell reproduction can produce a
mass of cells called a tumor.
• An abnormal mass of essentially normal cells is
called a benign tumor.
• More problematic are malignant tumors, masses
of cells that result from the reproduction of
cancer cells.
• Cancer is a disease caused by the severe
disruption of the mechanisms that normally
control the cell cycle.
• This disruption leads to uncontrolled cell division,
which if unchecked can result in death.
• The most dangerous characteristic of cancer cells is their
ability to spread.
• A malignant tumor displaces normal tissue as it grows. If a
malignant tumor is not killed or removed, it can spread into
surrounding tissues.
• More alarming still, cells may split off from the tumor and
travel to other parts of the body, where they can form new
tumors.
• The spread of cancer cells beyond their original site is called
metastasis (muh TAS tuh sis).
Cancer Treatment
• When possible, malignant tumors are removed by surgery.
However, it's difficult to successfully remove all traces of cancer
cells with surgery.
• To treat cancer at the cellular level, physicians sometimes use
radiation therapy or chemotherapy.
• Both of these treatments attempt to stop cancer cells from dividing.
– In radiation therapy, the parts of the body with cancerous tumors are
exposed to high-energy radiation, which disrupts cell division.
– Chemotherapy involves treating the patient with drugs that disrupt cell
division.
• Both radiation and chemotherapy can cause undesirable side
effects in normal body cells that divide fairly often.
– Radiation, for example, can damage cells of the ovaries or testes, causing
sterility.
– Intestinal cells or hair follicle cells can be affected by chemotherapy,
leading to nausea or hair loss.
Concept Check 9.4
1. List two differences between benign tumors and malignant
tumors.
2. How might drugs that interfere with mitosis be effective in
treating cancer?
3. How is cancer related to cell reproduction?