Cancer is a group of many related diseases that begin in cells, the body's basic building blocks. To understand cancer, it is helpful to know what happens when normal cells become cancerous.

The body is made up of many types of cells. Normally, cells grow and divide to produce more cells as they are needed to keep the body healthy. Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. The extra cells form a mass of tissue called a growth or tumor. Not all tumors are cancerous; tumors can be benign or malignant.

• Benign tumors are not cancer. 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. Most important, benign tumors are rarely a threat to life.

• Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control or order. Cancer cells invade and destroy the tissue around them. Cancer cells can also break away from a malignant tumor and enter the bloodstream or lymphatic system.

Blood vessels include a network of arteries, capillaries, and veins through which the blood circulates in the body. The lymphatic system carries lymph and white blood cells through lymphatic vessels (thin tubes) to all the tissues of the body. By moving through the bloodstream or lymphatic system, cancer can spread from the primary (original) cancer site to form new tumors in other organs. The spread of cancer is called metastasis.

Scientists have learned that cancer is caused by changes in genes that normally control the growth and death of cells. Certain lifestyle and environmental factors can change some normal genes into genes that allow the growth of cancer. Many gene changes that lead to cancer are the result of tobacco use, diet, exposure to ultraviolet (UV) radiation from the sun, or exposure to carcinogens (cancer-causing substances) in the workplace or in the environment. Some gene alterations are inherited (from one or both parents). However, having an inherited gene alteration does not always mean that the person will develop cancer; it only means that the chance of getting cancer is increased. Scientists continue to examine the factors that may increase or decrease a person's chance of developing cancer.

Although being infected with certain viruses, such as the human papillomavirus (HPV), hepatitis B and C, and human immunodeficiency virus (HIV), increases the risk of some types of cancer, cancer itself is not contagious. A person cannot catch cancer from someone who has this disease. Scientists also know that an injury or bruise does not cause cancer.

Although there is no guaranteed way to prevent cancer, people can reduce their risk (chance) of developing cancer by:

• Not using tobacco products • Choosing foods with less fat and eating more vegetables, fruits, and whole grains • Exercising regularly and maintaining a lean weight • Avoiding the harmful rays of the sun, using sunscreen, and wearing clothing that protects the skin • Talking with a doctor about the possible benefits of drugs proven to reduce the risk of certain cancers

Although many risk factors can be avoided, some, such as inherited conditions, are unavoidable. Still, it is helpful to be aware of them. It is also important to keep in mind that not everyone with a particular risk factor for cancer actually gets the disease; in fact, most do not. People who have an increased likelihood of developing cancer can help protect themselves by avoiding risk factors (see Question 2) whenever possible and by getting regular checkups so that, if cancer develops, it is likely to be found and treated early. Treatment is often more effective when cancer is detected early. Screening exams, such as sigmoidoscopy or the fecal occult blood test, mammography, and the Pap test, can detect precancerous conditions (which can be treated before they turn into cancer) and early-stage cancer.

The National Cancer Institute (NCI) is conducting many cancer prevention studies to explore ways to reduce the risk of developing cancer. These studies are evaluating dietary supplements, chemopreventive agents nutrition, personal behaviors, and other factors that may prevent cancer. More information about cancer prevention trials is available in the following NCI resources:

• Breast Cancer Prevention Studies • Selenium and Vitamin E Cancer Prevention Trial • The Study of Tamoxifen and Raloxifene (STAR): Questions and Answers

Cancer can cause a variety of symptoms. Possible signs of cancer include the following:

• New thickening or lump in the breast or any other part of the body • New mole or an obvious change in the appearance of an existing wart or mole • A sore that does not heal • Nagging cough or hoarseness • Changes in bowel or bladder habits • Persistent indigestion or difficulty swallowing • Unexplained changes in weight • Unusual bleeding or discharge

When these or other symptoms occur, they are not always caused by cancer. They can be caused by infections, benign tumors, or other problems. It is important to see a doctor about any of these symptoms or about other physical changes. Only a doctor can make a diagnosis. A person with these or other symptoms should not wait to feel pain because early cancer usually does not cause pain.

If symptoms occur, the doctor may perform a physical examination, order blood work and other tests, and/or recommend a biopsy. In most cases, a biopsy is the only way to know for certain whether cancer is present. During a biopsy, the doctor removes a sample of tissue from the abnormal area. A pathologist studies the tissue under a microscope to identify cancer cells.

Cancer treatment can include surgery, radiation therapy, chemotherapy, hormone therapy, and biological therapy. The doctor may use one method or a combination of methods, depending on the type and location of the cancer, whether the disease has spread, the patient's age and general health, and other factors. Because treatment for cancer can also damage healthy cells and tissues, it often causes side effects. Some patients may worry that the side effects of treatment are worse than the disease. However, patients and doctors generally discuss the treatment options, weighing the likely benefits of killing cancer cells and the risks of possible side effects. Doctors can suggest ways to reduce or eliminate problems that may occur during and after treatment.

Yes. Clinical trials are an important treatment option for many cancer patients. To develop new, more effective treatments, and better ways to use current treatments, the NCI is sponsoring clinical trials in many hospitals and cancer centers around the country. Clinical trials are a critical step in the development of new methods of treatment. Before any new treatment can be recommended for general use, doctors conduct clinical trials to find out whether the treatment is safe for patients and effective against the disease.

People interested in taking part in a clinical trial should talk with their doctor. Information about clinical trials is available from the NCI's Cancer Information Service (CIS)at 1–800–4–CANCER and in the NCI booklet Taking Part in Cancer Treatment Research Studies, which is available here .

This booklet describes how research studies are carried out and explains their possible benefits and risks. Further information about clinical trials is available here on the NCI's Web site. The Web site offers detailed information about specific ongoing treatment trials as well as trials focused on prevention, screening, and diagnosis by linking to PDQ®, the NCI's comprehensive cancer information database. The CIS also provides information from PDQ.

Having cancer does not always mean having pain. Whether a patient has pain may depend on the type of cancer, the extent of the disease, and the patient's tolerance for pain. Most pain occurs when the cancer grows and presses against bones, organs, or nerves. Pain may also be a side effect of treatment. However, pain can generally be relieved or reduced with prescription medicines or over-the-counter drugs recommended by the doctor. Other ways to reduce pain, such as relaxation exercises, may also be useful. Pain should not be accepted as an unavoidable part of having cancer. It is important for patients to talk about pain so steps can be taken to help relieve it. The fear of addiction or “losing control” should not stop patients from taking pain medication. Patients who take medications for cancer pain, as prescribed by their doctor, rarely become addicted to them. In addition, changing the dose or type of medication can usually help if the patient has troublesome side effects.

Before starting treatment, you may want a second opinion about your diagnosis and treatment plan. Many insurance companies will cover a second opinion if your doctor requests it. It may take some time and effort to gather medical records and arrange to see another doctor. Usually it is not a problem to take several weeks to get a second opinion. In most cases, the delay in starting treatment will not make treatment less effective. But some people with cancer need treatment right away. To make sure, you should discuss this delay with your doctor.

There are a number of ways to find a doctor for a second opinion:

1. Your doctor may refer you to one or more specialists. At cancer centers, several specialists often work together as a team.

2. NCI's Cancer Information Service, at 1-800-4-CANCER, can tell you about nearby treatment centers. Information Specialists also can provide online assistance through LiveHelp at cancer.gov

3. A local or state medical society, a nearby hospital, or a medical school can usually provide the names of specialists.

4. The American Board of Medical Specialties (ABMS) has a list of doctors who have had training and passed exams in their specialty. You can find this list in the Official ABMS Directory of Board Certified Medical Specialists. This directory is in most public libraries. Also, ABMS offers this information at http://www.abms.org. (Click on "Who's Certified.")

5. The NCI provides a fact sheet called "How To Find a Doctor or Treatment Facility If You Have Cancer."

6. Nonprofit organizations with an interest in cancer may be of help. See the NCI fact sheet "National Organizations That Offer Services to People With Cancer and Their Families."

Information originated from the National Cancer Institute’s website: cancer.gov

Bladder Cancer: Cancer that forms in tissues of the bladder (the organ that stores urine). Most bladder cancers are transitional cell carcinomas (cancer that begins in cells that normally make up the inner lining of the bladder). Other types include squamous cell carcinoma (cancer that begins in thin, flat cells) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). The cells that form squamous cell carcinoma and adenocarcinoma develop in the inner lining of the bladder as a result of chronic irritation and inflammation.

Treatment Options: Surgery, Radiation therapy, Chemotherapy, Biologic therapy

Breast Cancer: Cancer that forms in tissues of the breast. The most common type of breast cancer is ductal carcinoma, which begins in the lining of the milk ducts (thin tubes that carry milk from the lobules of the breast to the nipple). Another type of breast cancer is lobular carcinoma, which begins in the lobules (milk glands) of the breast. Invasive breast cancer is breast cancer that has spread from where it began in the breast ducts or lobules to surrounding normal tissue. Breast cancer occurs in both men and women, although male breast cancer is rare.

Treatment Options: Surgery, Radiation therapy, Chemotherapy, Hormone therapy, Targeted Therapy

Colon Cancer: Cancer that forms in the tissues of the colon (the longest part of the large intestine). Most colon cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

Rectal Cancer:: Cancer that forms in the tissues of the rectum (the last several inches of the large intestine closest to the anus).

Treatment Options: There are six types of standard treatment used to treat colon cancer:

• Surgery
• Radiofrequency ablation
• Cryosurgery
• Chemotherapy
• Radiation therapy
• Targeted therapy


There are four types of standard treatment used to treat Rectal Cancer:

• Surgery
• Radiation therapy
• Chemotherapy
• Targeted therapy

Endometrial cancer: Cancer that forms in the tissue lining the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a fetus develops). Most endometrial cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

Treatment Options: Surgery. Radiation therapy. Chemotherapy, Hormone therapy

Kidney cancer: Cancer that forms in tissues of the kidneys. Kidney cancer includes renal cell carcinoma (cancer that forms in the lining of very small tubes in the kidney that filter the blood and remove waste products) and renal pelvis carcinoma (cancer that forms in the center of the kidney where urine collects). It also includes Wilms tumor, which is a type of kidney cancer that usually develops in children under the age of 5.

Treatment Options: Surgery, Radiation Therapy, Chemotherapy, Biologic theraphy, Targeted therapy

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 bloodstream.

Treatment Options: Chemotherapy Radiation therapy, Chemotherapy with stem cell transplant, Targeted therapy

Lung cancer: Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.

Treatment Options: Surgery, Radiation therapy, Chemotherapy, Targeted therapy, Laser therapy. Photodynamic therapy (PDT), Cryosurgery, Electrocauter, Watchful waiting

Melanoma: A form of cancer that begins in melanocytes (cells that make the pigment melanin). It may begin in a mole (skin melanoma), but can also begin in other pigmented tissues, such as in the eye or in the intestines.

Treatment Options: Surgery, Chemotheraphy, Radiation Therapy, Biologic Therapy, Targeted Therapy

Non-Hodgkin lymphoma: Any of a large group of cancers of lymphocytes (white blood cells). Non-Hodgkin lymphomas can occur at any age and are often marked by lymph nodes that are larger than normal, fever, and weight loss. There are many different types of non-Hodgkin lymphoma. These types can be divided into aggressive (fast-growing) and indolent (slow-growing) types, and they can be formed from either B-cells or T-cells. B-cell non-Hodgkin lymphomas include Burkitt lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma, follicular lymphoma, immunoblastic large cell lymphoma, precursor B-lymphoblastic lymphoma, and mantle cell lymphoma. T-cell non-Hodgkin lymphomas include mycosis fungoides, anaplastic large cell lymphoma, and precursor T-lymphoblastic lymphoma. Lymphomas that occur after bone marrow or stem cell transplantation are usually B-cell non-Hodgkin lymphomas. Prognosis and treatment depend on the stage and type of disease. Also called NHL.

Treatment Options: Radiation therapy, Chemotherapy, Targeted therapy, Plasmapheresis, Biologic therapy, Watchful waiting

Pancreatic cancer: A disease in which malignant (cancer) cells are found in the tissues of the pancreas. Also called exocrine cancer.

Treatment Options: Surgery, Chemotherapy, hormone therapy, hepatic arterial occlusion or chemoembolization, targeted therapy, supportive care

Prostate cancer: Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men.

Treatment Options: Watchful waiting or surveillance, surgery, radiation therapy, hormone therapy, chemotherapy, biologic therapy, bisphosphonate therapy, targeted therapy

Thyroid cancer: Cancer that forms in the thyroid gland (an organ at the base of the throat that makes hormones that help control heart rate, blood pressure, body temperature, and weight). Four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. The four types are based on how the cancer cells look under a microscope.

Treatment Options: Surgery, Radiation Therapy, including radioactive iodine therapy, chemotrherapy, thyroid hormone therapy, targeted therapy

Surgery is an operation to remove cancer. The side effects of surgery depend on many factors, including the size and location of the tumor, the type of operation, and the patient's general health. Patients have some pain after surgery, but this pain can be controlled with medicine. It is also common for patients to feel tired or weak for a while after surgery. Patients may worry that having a biopsy or other type of surgery for cancer will spread the disease. This is a very rare occurrence because surgeons take special precautions to prevent cancer from spreading during surgery. Also, exposing cancer to air during surgery does not cause the disease to spread.

Radiation therapy (also called radiotherapy) uses high-energy rays to kill cancer cells in a targeted area. Radiation can be given externally by a machine that aims radiation at the tumor area. It can also be given internally; needles, seeds, wires, or catheters containing a radioactive substance are placed directly in or near the tumor. Radiation treatments are painless. The side effects are usually temporary, and most can be treated or controlled. Patients are likely to feel very tired, especially in the later weeks of treatment. Radiation therapy may also cause a decrease in the number of white blood cells, which help protect the body against infection. With external radiation, it is also common to have temporary hair loss in the treated area and for the skin to become red, dry, tender, and itchy. There is no risk of radiation exposure from coming in contact with a patient undergoing external radiation therapy. External radiation does not cause the body to become radioactive. With internal radiation (also called implant radiation), a patient may need to stay in the hospital, away from other people, while the radiation level is highest. Implants may be permanent or temporary. The amount of radiation in a permanent implant goes down to a safe level before the person leaves the hospital. With a temporary implant, there is no radioactivity left in the body after the implant is removed.

Learn more about radiation therapy: Radiation Therapy

Chemotherapy is the use of drugs that kill cancer cells throughout the body. Healthy cells can also be harmed, especially those that divide quickly. The doctor may use one drug or a combination of drugs. The side effects of chemotherapy depend mainly on the drug(s) and the dose(s) the patient receives. Hair loss is a common side effect of chemotherapy; however, not all anticancer drugs cause loss of hair. Anticancer drugs may also cause temporary fatigue, poor appetite, nausea and vomiting, diarrhea, and mouth and lip sores. Drugs that prevent or reduce nausea and vomiting can help with some of these side effects. Normal cells usually recover when chemotherapy is over, so most side effects gradually go away after treatment ends.

Hormone therapy is used to treat certain cancers that depend on hormones for their growth. It works by keeping cancer cells from getting or using the hormones they need to grow. This treatment may include the use of drugs that stop the production of certain hormones or that change the way hormones work. Another type of hormone therapy is surgery to remove organs that make hormones. For example, the ovaries may be removed to treat breast cancer, or the testicles may be removed to treat prostate cancer. Hormone therapy can cause a number of side effects. Patients may feel tired, or have fluid retention, weight gain, hot flashes, nausea and vomiting, changes in appetite, and, in some cases, blood clots. Hormone therapy may also cause bone loss in premenopausal women. Depending on the type of hormone therapy used, these side effects may be temporary, long lasting, or permanent.

Biological therapy uses the body's immune system, directly or indirectly, to fight disease and to lessen some of the side effects of cancer treatment. Monoclonal antibodies, interferon, interleukin-2, and colony-stimulating factors are some types of biological therapy. The side effects caused by biological therapy vary with the specific treatment. In general, these treatments tend to cause flu-like symptoms, such as chills, fever, muscle aches, weakness, loss of appetite, nausea, vomiting, and diarrhea. Patients also may bleed or bruise easily, get a skin rash, or have swelling. These problems can be severe, but they go away after the treatment stops.