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WHAT IS CANCER?


Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body.


Cancer is not just one disease but many diseases. Tere are more than 100 different types of cancer. Most cancers are named for the organ or type of cell where they start. For example, cancer that begins in the colon is called colon cancer; cancer that begins in the breast is called breast cancer.


Cancer types can be grouped into broader categories. Te main categories of cancer include the following:


• Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs


• Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.


• Leukemia is cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.


• Lymphoma and myeloma are cancers that begin in the cells of the immune system.


• Central nervous system cancers begin in the tissues of the brain and spinal cord.


Origins of Cancer


All cancers begin in cells, the body’s basic unit of life. To understand cancer, it’s helpful to know what happens when normal cells become cancer cells.


Te body is made up of many types of cells. Tese cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells.


However, sometimes this orderly process goes wrong. Te genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should, and new cells form when the body does not need them. Te extra cells may form a mass of tissue called a tumor.


Not all tumors are cancerous. Tumors can be benign or malignant.


There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell where they start.


For example, cancer that starts in the colon is called colon cancer, and cancer that starts in the breast is called breast cancer.


Benign tumors aren’t cancerous. Tey can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body.


Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. Te spread of cancer from one part of the body to another is called metastasis.


Some cancers do not form tumors. For example, leukemia is a cancer of the bone marrow and blood.


The information on this page comes from the National Cancer Institute.


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