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
through the blood and lymph systems.
Cancer is not just one disease but many diseases. There are more than 100
different types of cancer. Most cancers are named for the organ or type of
cell in which they start - for example, cancer that begins in the colon is
called colon cancer; cancer that begins in basal cells of the skin is called
basal cell carcinoma.
Cancer types can be grouped into broader categories. The main categories of
cancer include:
Carcinoma - cancer that begins in the skin or in tissues that line or
cover internal organs.
Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
Leukemia - 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 - cancers that begin in the cells of the immune system.
Central nervous system cancers - cancers that begin in the tissues of
the brain and spinal cord.
(For definitions of other cancer-related terms, see NCI's
Dictionary
of Cancer Terms.)
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.
The body is made up of many types of cells. These 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. The 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. The
extra cells may form a mass of tissue called a tumor.
(Image from
Understanding Cancer Series: Cancer.)
Not all tumors are cancerous; tumors can be benign or malignant.
Benign tumors aren't cancerous. They 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. The 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.
Cancer Statistics
A new report from the nation's leading cancer organizations shows that, for
the first time since the report was first issued in 1998, both incidence and
death rates for all cancers combined are decreasing for both men and women,
driven largely by declines in some of the most common types of cancer. (Read
more about the Annual Report.)
Estimated new cases and deaths from cancer in the United States in 2009:
New cases: 1,479,350 (does not include nonmelanoma skin cancers)
Deaths: 562,340
NCI's Cancer Stat Fact Sheets provide frequently requested cancer statistics for a number of cancer types.
Additional Information
Find a type of cancer:
A to Z List of Cancers
Cancers by Body Location/System
Cancers that are diagnosed with the greatest frequency in the United States
are listed below. (Read more about
Common Cancer Types.)
Bladder Cancer
Melanoma
Breast Cancer
Non-Hodgkin Lymphoma
Colon and Rectal Cancer
Pancreatic Cancer
Endometrial Cancer
Prostate Cancer
Kidney (Renal Cell)
Cancer
Skin Cancer (Nonmelanoma)
Leukemia
Thyroid Cancer
Lung Cancer
More cancer topics:
Cancer Prevention
Cancer Genetics
Cancer Causes and Risk Factors
Screening and Testing to Detect Cancer
Cancer Treatment
Coping with Cancer
Cancer Statistics
Clinical Trials
Cancer Publications
The risk of developing many types of cancer can be reduced by practicing
healthy lifestyle habits, such as eating a healthy diet, getting regular
exercise, and not smoking. Also, the sooner a cancer is found and treatment
begins, the better the chances are that the treatment will be successful.
Contact Us for Help
NCI cancer information specialists can answer your questions about cancer
and help you with quitting smoking. They can also help you with using this
Web site and can tell you about NCI's printed and electronic materials.
Contact us.
SOURCE:
http://www.cancer.gov/cancertopics/what-is-cancer
