About Cancer

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 the second-leading cause of death in the United States. But survival rates are improving for many types of cancer thanks to improvements in cancer screening and cancer treatment.


Signs and symptoms caused by cancer will vary depending on what part of the body is affected. Some general signs and symptoms associated with, but not specific to, cancer include:

  • Fatigue
  • Fever
  • Lump or thickening that can be felt under the skin
  • Pain
  • 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
  • Hoarseness
  • Persistent indigestion or discomfort after eating


Cancer is caused by damage (mutations) to the DNA within cells. Your DNA contains a set of instructions for your cells, telling them how to grow and divide. Normal cells often develop mutations in their DNA, but they have the ability to repair most of these mutations. Or, if they can’t make the repairs, the cells often die. However, certain mutations aren’t repaired, causing the cells to grow and become cancerous. Mutations also cause cancer cells to live beyond their normal cell life span. This causes the cancerous cells to accumulate.

In some cancers, accumulating cells form a tumor. But not all cancers form tumors. For example, leukemia is a cancer that involves blood, bone marrow, the lymphatic system and the spleen, but doesn’t form a single mass or tumor.

The initial genetic mutation is just the beginning of the process by which cancer develops. Scientists believe you need a number of changes within a cell in order to develop cancer, including:

  • An initiator to cause a genetic mutation. Sometimes you’re born with this genetic mutation. Other times a genetic mutation is caused by forces within your body, such as hormones, viruses and chronic inflammation. Genetic mutations can also be caused by forces outside of your body, such as ultraviolet (UV) light from the sun or cancer-causing chemicals (carcinogens) in your environment.
  • A promoter to cause rapid cell growth. Promoters take advantage of genetic mutations created by initiators. Promoters cause cells to divide more rapidly. This could lead to an accumulation of cells, such as a tumor. Promoters could be inherited, could come from inside your body or could come from outside your body.
  • A progressor to cause cancer to become aggressive and spread. Without a progressor a tumor may remain benign and localized. Progressors make cancers more aggressive, more likely to invade and destroy nearby tissue, and more likely to spread to other parts of your body. Like initiators and promoters, progressors could be inherited or they could come from environmental sources.

Your genetic makeup, forces within your body, your lifestyle choices and your environment can all set the stage for cancer or help complete the process once it’s started. For instance, if you’ve inherited a genetic mutation that predisposes you to cancer, you may be more likely than other people to develop cancer when exposed to a certain cancer-causing substance. The genetic mutation begins the cancer process, and the cancer-causing substance could play a role in further cancer development. Likewise, smokers who work with asbestos are more likely to develop lung cancer than are smokers who don’t work with asbestos. That’s because tobacco smoke and asbestos both play roles in cancer development.

Risk factors

While doctors have an idea of what can put you at risk of cancer, the majority of cancers occur in people who don’t have any known risk factors. Factors known to increase your risk of cancer include:

Your age
Cancer can take decades to develop. That’s why most people diagnosed with cancer are 55 or older. By the time a cancerous mass is detected, it’s likely that 100 million to 1 billion cancer cells are present, and the original cancer may have been growing for five years or more. While it’s more common in older adults, cancer isn’t exclusively an adult disease — cancer can be diagnosed at any age.

Your habits
Certain lifestyle choices are known to increase your risk of cancer. Smoking, drinking more than one drink a day (for women) or two drinks a day (for men), excessive exposure to the sun or frequent blistering sunburns, and having unsafe sex can contribute to cancer. You can break these habits to lower your risk of cancer — though some habits are easier to break than others.

Your family history
Only about 10 percent of cancers are due to an inherited condition. If cancer is common in your family, it’s possible that mutations are being passed from one generation to the next. You might be a candidate for genetic screening to see whether you have inherited mutations that might increase your risk of cancer. Keep in mind that having an inherited genetic mutation doesn’t necessarily mean you’ll get cancer.

Your health conditions
Some chronic health conditions, such as ulcerative colitis, can markedly increase your risk of developing certain cancers. Talk to your doctor about your risk.

Your environment
The environment around you may contain harmful chemicals that can increase your risk of cancer. Even if you don’t smoke, you might inhale secondhand smoke if you go places where people are smoking or you live with someone who smokes. Chemicals in your home or work place, such as asbestos and benzene, also are associated with an increased risk of cancer.


Cancer screening
Diagnosing cancer at its earliest stages often provides the best chance for a cure. With this in mind, talk with your doctor about what types of cancer screening may be appropriate for you. For a few cancers, studies show screening tests can save lives by diagnosing cancer early. For other cancers, screening tests are reserved for people with the highest risk. Discuss your cancer risks with your doctor.

The American Cancer Society generally recommends screening for the following cancers in adults considered to have an average risk of cancer:

Type of cancer Who should consider screening?
Breast cancer Women 40 and older
Cervical cancer Women 21 or older, or beginning three years after first sexual intercourse
Colon cancer Men and women 50 and older
Prostate cancer Men 50 and older

Screening tests and procedures have risks and benefits. Discuss these with your doctor to determine whether screening is right for you.

Cancer diagnosis
Your doctor may use one or more approaches to diagnose cancer:

  • 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 any abnormalities, such as changes in skin color or enlargement of an organ, that may indicate cancer.
  • Laboratory tests. Laboratory tests, such as urine and blood tests, may help your doctor identify abnormalities that can be caused by cancer. For instance, in people with leukemia, a common blood test called complete blood count (CBC) may reveal an unusual number of white blood cells.
  • Imaging tests. Imaging tests allow your doctor to examine your bones and internal organs in a noninvasive way. Imaging tests used in diagnosing cancer may include computerized tomography (CT) scan, bone scan, magnetic resonance imaging (MRI), ultrasound and X-ray, among others.
  • Biopsy. During a biopsy, your doctor collects a sample of cells for testing in the laboratory. There are several different ways of collecting a biopsy sample. Which biopsy procedure is right for you depends on your type of cancer and its location. In most cases, a biopsy is the only way to definitively diagnose cancer. In the laboratory, doctors look at biopsy samples under the microscope. Normal cells look uniform, with similar sizes and orderly organization. Cancer cells look less orderly, with varying sizes and without apparent organization.

Cancer stages
Once cancer is diagnosed, your doctor will work to determine the extent, or stage, of your cancer. Your doctor uses your cancer’s stage to determine your treatment options and your chances for a cure. Staging tests and procedures may include imaging tests, such as a bone scans or X-rays to see if cancer has spread to other parts of the body.

Cancer stages are generally indicated by Roman numerals — I through IV, with higher numerals indicating more advanced cancer. In some cases, cancer stage is indicated using letters or words.


Cancer and its treatment can cause several complications, including:

  • Side effects of cancer treatment. Cancer treatments frequently cause side effects that can be temporary or that can last for months and years after treatment. Many side effects can be treated or managed. Ask your doctor what types of side effects you can expect from your cancer treatment. You may factor these side effects into your treatment decisions.
  • Unusual immune system reactions to cancer. In some cases your body’s immune system may react to the presence of cancer by attacking healthy cells. Called paraneoplastic syndromes, these unusual reactions can lead to a variety of signs and symptoms, such as fever, difficulty walking and seizures.
  • Cancer that spreads. As cancer advances it may spread (metastasize) to other parts of the body. Where cancer spreads depends on the type of cancer. In general, cancer that has spread may be managed, but can’t be cured.
  • Cancer that returns. Cancer survivors have a risk of cancer recurrence. Some cancers are more likely to recur than others. Ask your doctor about what you can do to reduce your risk of cancer recurrence. Your doctor may devise a follow-up care plan for you after treatment. This plan may include periodic scans and exams in the months and years after your treatment to look for cancer recurrence.


Many cancer treatments are available. Your treatment options will depend on several factors, such as the type and stage of your cancer, your general health and your preferences. Together you and your doctor can weigh the benefits and risks of each cancer treatment to determine which is best for you.

Goals of cancer treatment
Cancer treatments are used in various ways, such as:

  • Treatment to kill or remove cancer cells (primary treatment). The goal of a primary treatment is to remove the cancer from your body or kill the cancer cells. Any cancer treatment can be used as a primary treatment, but the most common primary cancer treatment for the most common cancers is surgery. If your cancer is particularly sensitive to radiation therapy or chemotherapy, you may receive one of those therapies as your primary treatment.
  • Treatment to kill any remaining cancer cells (adjuvant therapy). The goal of adjuvant therapy is to kill any cancer cells that may remain after primary treatment. Any cancer treatment can be used as an adjuvant therapy. Common adjuvant therapies include chemotherapy, radiation therapy and hormone therapy.
  • Treatment to manage side effects of cancer and its treatment (palliative care). The goal of palliative care is to decrease pain or other symptoms and help you maintain quality of life during and after cancer treatment. Palliative treatments may help relieve side effects of treatment or signs and symptoms caused by cancer itself.

Cancer treatments
Doctors have many tools when it comes to treating cancer. Cancer treatment options include:

  • Surgery. The goal of surgery is to remove the cancer or as much of the cancer as possible.
  • Chemotherapy. Chemotherapy uses drugs to kill cancer cells.
  • Radiation therapy. Radiation therapy uses high-powered energy beams, such as X-rays, to kill cancer cells. Radiation treatment can come from a machine outside your body (external beam radiation) or it can be placed inside your body (brachytherapy).
  • Blood stem cell transplant. Blood stem cell transplant is also known as bone marrow transplant. Your bone marrow is the material inside your bones that makes blood cells from blood stem cells. A blood stem cell transplant can use your own stem cells or stem cells from a donor.
  • Biological therapy. Biological therapy uses your body’s immune system to fight cancer. Cancer can survive unchecked in your body because your immune system doesn’t recognize it as an intruder. Biological therapy can help your immune system “see” the cancer and attack it.
  • Hormone therapy. Some types of cancer are fueled by your body’s hormones. Examples include breast cancer and prostate cancer. By removing those hormones from the body, the cancer cells may die.
  • Targeted drug therapy. Targeted drug treatment targets specific abnormalities within cancer cells that allow them to survive.
  • Clinical trials. Clinical trials are studies to investigate new ways of treating cancer. Thousands of cancer clinical trials are under way.

Other treatments may be available to you, depending on your type of cancer.


There’s no certain way to prevent cancer. But doctors have identified several ways of reducing your cancer risk, such as:

  • Stop smoking. If you smoke, quit. If you don’t smoke, don’t start. Smoking is linked to several types of cancer — not just lung cancer. Quitting now will reduce your risk of cancer in the future.
  • Avoid excessive sun exposure. Harmful ultraviolet (UV) rays from the sun can increase your risk of skin cancer. Limit your sun exposure by staying in the shade, wearing protective clothing or applying sunscreen.
  • Eat a healthy diet. Choose a diet rich in fruits and vegetables. Select whole grains and lean proteins.
  • Exercise most days of the week. Regular exercise is linked to a lower risk of cancer. Aim for 30 minutes of exercise most days of the week. If you haven’t been exercising regularly, start out slowly and work your way up to 30 minutes or longer.
  • Maintain a healthy weight. Being overweight or obese may increase your risk of cancer. Work to achieve and maintain a healthy weight through a combination of a healthy diet and regular exercise.
  • Schedule cancer screening exams. Talk to your doctor about what types of cancer screening exams are best for you, based on your risk factors.
  • Ask your doctor about immunizations. Certain viruses increase your risk of cancer. Immunizations 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. Ask your doctor whether immunization against these viruses is appropriate for you.

A cancer diagnosis is a devastating event that can change your life forever. Each person finds his or her own way of coping with the emotional and physical changes cancer brings. But when you’re first diagnosed with cancer, sometimes it’s difficult to know what to do next. Here are some ideas to help you cope:

  • Find out all you can about your cancer. Write down all the questions you have about your cancer so that you can ask them at your next appointment. Ask your health care team for reliable resources for further information about your diagnosis. The more you know about your cancer and your treatment options, the more confident you’ll feel when it comes time to make decisions about your treatment.
  • Find someone to talk to. Find a trusted person you can talk with about how you’re feeling. Perhaps that person is a close friend or family member who is a good listener. Other people who can help include clergy members and counselors. Other people with cancer can offer unique insight. Contact the American Cancer Society for information on cancer support groups in your community. Internet message boards can also work as virtual support groups. Start with the message boards on the American Cancer Society’s Web site.
  • Stay connected to family and friends. Your family and friends provide an important support network for you during cancer treatment. Often family and friends want to help, but they aren’t sure how. Think of ways you might like assistance, even if it’s just being there to listen when you have a bad day. Offer these as suggestions when family and friends ask if there’s anything they can do to help.
  • Take care of yourself. Do what you can to take care of yourself during cancer treatment. Eat a healthy diet full of fruits and vegetables. Get enough sleep so that you wake feeling rested. Find time for activities that can reduce stress, such as relaxation exercises, listening to music and writing your thoughts in a journal.

Alternative medicine

No alternative cancer treatments have been proved to cure cancer. But alternative medicine options may help you cope with side effects of cancer and cancer treatment, such as fatigue, nausea and pain.

Talk with your doctor about what alternative medicine options may offer some benefit. He or she can also discuss whether these therapies are safe for you or whether they may interfere with your cancer treatment.

Some alternative medicine options found to be helpful for people with cancer include:

  • Acupuncture
  • Hypnosis
  • Massage
  • Meditation
  • Relaxation techniques