Defining 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 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 melanocytes of the skin is called melanoma.
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. There are a number of subtypes of carcinoma, including adenocarcinoma, basal cell carcinoma, squamous cell carcinoma, and transitional cell carcinoma.
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.)
To find out more about a specific type of cancer, see the A to Z List of Cancers or the list of Cancers by Body Location/System.
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.
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 report from the nation's leading cancer organizations shows that rates of death in the United States from all cancers for men and women continued to fall between 2005 and 2009, the most recent reporting period available. (Read more about the Annual Report.)
Estimated new cases and deaths from cancer in the United States in 2013:
New cases: 1,660,290 (does not include nonmelanoma skin cancers)
Deaths: 580,350
NCI's Cancer Stat Fact Sheets provide frequently requested cancer statistics for a number of cancer types.
Additional Information
Cancers that are diagnosed with the greatest frequency in the United States are listed below. (Read more about Common Cancer Types.)
Bladder Cancer
Breast Cancer
Colon and Rectal Cancer
Endometrial Cancer
Kidney (Renal Cell) Cancer
Leukemia
Lung Cancer
Melanoma
Non-Hodgkin Lymphoma
Pancreatic Cancer
Prostate Cancer
Thyroid 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.
We Can Answer Your Questions1-800-4-CANCER
How Many People Are Expected to Die of Cancer?
This year about 564,800 Americans are expected to die of cancer—more than 1,500 people a day. Cancer is the second leading cause of death in the US, exceeded only by heart disease. One of every four deaths in the US is from cancer. Since 1990, there have been approximately 5 million cancer deaths.
This year about 564,800 Americans are expected to die of cancer—more than 1,500 people a day. Cancer is the second leading cause of death in the US, exceeded only by heart disease. One of every four deaths in the US is from cancer. Since 1990, there have been approximately 5 million cancer deaths.
What Is the National Cancer Death Rate?
Between 1991 and 1995, the national cancer death rate fell 2.6%. Most of the decline can be attributed to decreases in mortality from cancers of the lung, colon-rectum, and prostate in men, and breast, colon-rectum, and gynecologic sites in women. The declines in mortality were greater in men than in women, largely because of changes in lung cancer rates; greater in young patients than in older patients; and greater in African Americans than in whites although mortality rates remain higher in African Americans.
Between 1991 and 1995, the national cancer death rate fell 2.6%. Most of the decline can be attributed to decreases in mortality from cancers of the lung, colon-rectum, and prostate in men, and breast, colon-rectum, and gynecologic sites in women. The declines in mortality were greater in men than in women, largely because of changes in lung cancer rates; greater in young patients than in older patients; and greater in African Americans than in whites although mortality rates remain higher in African Americans.
How Many People Are Surviving Cancer?
In the early 1900s, few cancer patients had any hope of long-term survival. In the 1930s, about one in four was alive five years after treatment. About 491,400 Americans, or 4 of 10 patients who get cancer this year, are expected to be alive five years after diagnosis.
In the early 1900s, few cancer patients had any hope of long-term survival. In the 1930s, about one in four was alive five years after treatment. About 491,400 Americans, or 4 of 10 patients who get cancer this year, are expected to be alive five years after diagnosis.
This 4 in 10, or about 40% is called the "observed" survival rate. When adjusted for normal life expectancy (factors such as dying of heart disease, accidents, and diseases of old age), a "relative" 5-year survival rate of 58% is seen for all cancers. Five-year relative survival rates, commonly used to monitor progress in early detection and treatment of cancer, include persons who are living five years after diagnosis, whether in remission, disease-free, or under treatment. While these rates provide some indication about the average survival experience of cancer patients in a given population, they are less informative when used to predict individual prognosis.
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