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Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. Cancer also has the ability to spread throughout your body.


Cancer is caused by changes (mutations) to the DNA within cells. Each cell’s DNA contains a set of instructions telling it how to grow and divide. Errors in these instructions can allow a cell to become cancerous.

Most commonly, a gene mutation may instruct a healthy cell to do one of the following:

  • Grow too fast. The cell grows and divides more rapidly than normal. This creates many new cells that have the same mutation.
  • Forget to apply the brakes. Normal cells know when to stop growing. Cancer cells lose such control. They continue to grow and accumulate.
  • Overlook DNA errors. Specialized genes called repair genes look for errors in a cell’s DNA and make corrections. A mutation in a repair gene may prevent an error from being corrected.


  • Age. Because cancer can take decades to develop, it’s most common in people age 65 and older. However, it can occur at any age.
  •  Habits. Certain lifestyle choices are known to increase your risk of cancer. Smoking, excessive alcohol use, excessive exposure to the sun, being overweight, lack of exercise, and having unsafe sex can contribute to cancer.
  • Family history. Only a small portion of cancers are inherited. Having an inherited genetic mutation increases your risk but doesn’t necessarily mean you’ll get cancer.
  • Health. Some chronic conditions can markedly increase your risk of developing certain cancers. Ulcerative colitis, for example, significantly increases the risk of colon cancer.
  • Environment. Harmful chemicals in the environment can increase your risk of cancer. Examples include secondhand smoke or chemicals such as asbestos and benzene.


  • Fatigue
  • Lump or area of thickening that can be felt under the skin
  • Weight changes, including unintended loss or gain
  • Skin changes, such as yellowing, darkening or redness of the skin, sores that won’t heal, or changes to existing moles
  • Changes in bowel or bladder habits
  • Persistent cough
  • Difficulty swallowing or hoarseness
  • Persistent indigestion or discomfort after eating
  • Persistent, unexplained muscle or joint pain
  • Persistent, unexplained fevers or night sweats


Physical exam
Your doctor may feel areas of your body for lumps that may indicate a tumor. During a physical exam, he or she may look for abnormalities, such as changes in skin color or enlargement of an organ.

Laboratory tests
Laboratory tests, such as urine and blood tests, may help your doctor identify abnormalities associated with cancer. For instance, in people with leukemia, a common blood test called a complete blood count (CBC) may reveal an unusual number of white blood cells.

Imaging tests
Imaging tests used in diagnosing cancer may include a computerized tomography (CT) scan, bone scan, magnetic resonance imaging (MRI), ultrasound and X-ray, among others. These tests can identify tumors and other abnormalities associated with cancer.

A doctor collects a sample of cells for testing in the laboratory. There are several ways of doing this, depending on the type of cancer and its location. In most cases, a biopsy is the only way to definitively diagnose cancer. Under a microscope, cancer cells look less orderly than normal cells, with varying sizes and shapes.


Treatment depends, in part, on the type of cancer.


The goal is to remove cancer or as much of it as possible.

Chemotherapy uses medications to kill cancer cells. There are many chemotherapy drugs. Certain drugs are more effective for certain cancers

Radiation therapy. Radiation therapy involves the use of high-powered energy beams, such as X-rays, to kill cancer cells.

Stem cell transplant. 
Also known as bone marrow transplant, this procedure involves transplanting your own stem cells or stem cells from a donor into your bone marrow. This is done to replenish the marrow and encourage the growth of healthy new blood cells after cancerous cells are destroyed by chemotherapy.

Biological therapy. Biological therapy uses your body’s immune system to fight cancer. It helps your immune system “see” cancer and attack it.

Hormone therapy. 
Some types of cancer, such as breast and prostate cancer, are fueled by your body’s hormones. Removing those hormones or blocking their effects may cause the cancer cells to stop growing.


  • Stop smoking. Smoking is linked to several types of cancer — not just lung cancer.
  • Avoid excessive sun exposure. Harmful ultraviolet (UV) rays from the sun can increase your risk of skin cancer. When outside, wear protective clothing or use sunscreen.
  • Eat a healthy diet. Eat plenty of fruits and vegetables, which contain beneficial nutrients. Opt for whole grains and lean proteins.
  • Exercise. Regular exercise is linked to a lower risk of cancer. Aim for at least 30 minutes of exercise most days of the week.
  • Maintain a healthy weight. Being overweight or obese can increase your risk of cancer. Lose weight through a combination of a healthy diet and regular exercise.
  • Limit alcohol. If you choose to drink alcohol, limit yourself to one drink a day if you’re a healthy woman or a man over age 65, and two drinks a day if you’re a healthy man, age 65 and younger.
  • Get cancer screening exams. Talk to your doctor about what screening exams are best for you based on your risk factors.
  • Be up to date on your immunizations. Certain viruses increase your risk of cancer. Vaccinations may help prevent those viruses, including hepatitis B, which increases the risk of liver cancer, and human papillomavirus (HPV), which increases the risk of cervical cancer and other cancers.

        Excerpt From: The Mayo Clinic. “Mayo Clinic A to Z Health Guide”.

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