Cancer is the uncontrollable growth of cells. Cells are the basic building blocks of all living organisms. There are over 10 trillion cells in the human body. Normal cells have an orderly life cycle. They divide and multiply only when they need to and they die when they are damaged or no longer function properly. Cancer cells lose the ability to control their growth. They divide rapidly, creating new cancer cells, and do not die, even when they are damaged. These fast growing cells can eventually form a solid mass or lump called a malignant tumor. A tumor may be benign or malignant.
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Benign tumors are not cancerous and can usually be removed. They grow locally, meaning they remain in the part of the body where they form and do not invade healthy tissue or spread throughout the body.
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Malignant tumors are cancerous. As they grow, they can invade (grow through) nearby healthy tissues and organs, and ultimately impair organ function. Malignant tumors can also invade the lymphatic system and metastasize (spread) to nearby lymph nodes, or even get into the bloodstream and travel to distant organs, such as the lungs, liver and brain.
Cancers are named for the part of the body where the tumor first started growing. This area is known as the cancer's "primary site." For example, breast cancer that has spread to the lung is still called breast cancer. Each specific type of cancer exhibits different characteristics and responds to different treatments. There are five main classifications of cancer:
About half of all men and one third of all women will be diagnosed with cancer in their lifetimes. A healthy lifestyle with a good diet and plenty of physical activity, along with avoidance of harmful substances such as tobacco, excessive alcohol, and ultraviolet (UV) rays, can help reduce this risk and keep your cells functioning normally.
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