Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade different tissues in the body. Normally, cells grow and divide to form new cells as the body needs them. As cells grow old, they die and the new cells take their place. If new cells form when the body does not need them, or old cells do not die when they should, these extra cells can form a mass of tissue called a growth or tumor.
Tumors can be either benign or malignant. Benign tumors are not cancerous and can usually be removed and not grow back. They are rarely life-threatening and do not spread to other parts of the body. Malignant tumors, however, are cancerous. If they are removed, they sometimes can grow back and can often spread to other parts of the body.
Malignant tumors are generally more serious and can be life-threatening.
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, lung cancer starts in the lung, and colon cancer starts in the colon.
Cancer types can be grouped into broader categories. The main categories of cancer include:
- Cancer that begins in the skin or in tissues that line or cover internal organs.
- Cancer that begins in bone, cartilage, fat, muscle, blood vessels or other connective or supportive tissue.
- 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.
If cancer spreads and forms a new tumor in another part of the body, the new tumor has the same name as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are still breast cancer cells. The new tumor is defined as metastatic breast cancer and is treated as breast cancer, not bone cancer.
It is often difficult for doctors to explain why one person may develop cancer and another does not. However, research shows that certain risk factors can increase the chance that a person will develop cancer. The most common risk factors for cancer include:
- Growing older
- This is the most important risk factor, since a majority of cancers occur in people over the age of 65.
- People who smoke are more likely to develop cancer of the lung, larynx, mouth, esophagus, bladder, kidney, throat, stomach, pancreas or cervix.
- Ultraviolet (UV) radiation comes from the sun and causes skin damage that can lead to skin cancer.
- Ionizing radiation
- This kind of radiation comes from radioactive fallout and radon gas, and people may have an increased risk of cancer of the thyroid, breast, lung or stomach.
- Certain chemicals and other substances
- People who have certain jobs, such as painters, may be exposed to chemicals that have an increased risk of cancer.
- Viruses and bacteria
- If people are infected with certain viruses or bacteria, such as HIV or Helicobacter pylori, they may have an increased risk of developing cancer.
- Certain hormones
- Women that are prescribed hormones during menopause to help control problems such as hot flashes may be at increased risk of breast cancer.
- Family history
- Some changes in genes are passed from parent to child and are present at birth.
- If a person drinks more than two drinks a day for many years, they may have an increased chance of developing cancers of the mouth, throat, esophagus, larynx, liver and breast.
- Poor diet, lack of physical activity or being overweight
- People who have a diet high in fat have an increased risk of colon, uterus and prostate cancer; a lack of physical activity and being overweight are risk factors for developing breast, colon, esophagus, kidney and uterus cancers.
Cancer can cause many different types of symptoms and often depend on the type of cancer. The following are some cancer symptoms:
- Thickening or lump in the breast or any other part of the body
- A new mole or a change in an existing mole
- A sore that does not heal
- Hoarseness or a cough that does not go away
- Changes in bowel or bladder habits
- Discomfort after eating
- A hard time swallowing
- Weight gain or loss with no known reason
- Unusual bleeding or discharge
- Feeling weak or very tired
Doctors will often ask about a person’s medical history, perform a physical exam and may order special lab tests, x-rays or procedures to determine if a person has cancer:
- Lab tests
- Blood, urine or other fluids may be tested to help doctors make a diagnosis. These tests can show if there are any problems with organs or if there are tumor markers, which are high amounts of substances that may be a sign of cancer.
- This test is the most common for a doctor to view any changes in the organs or bones inside the body.
- CT scan
- A series of detailed pictures of the organs are taken with this test.
- Radionuclide scan
- A small amount of radioactive material is injected into a person’s bloodstream, and a scanner then takes pictures of bones or organs.
- An ultrasound device sends out sound waves that bounce off tissues in the body to detect any changes.
- A strong magnet is linked to a computer and is used to take detailed pictures of areas in the body where there is a concern of cancer.
- PET scan
- A small amount of radioactive material is injected into a person’s bloodstream, and pictures are taken to identify high areas of activity which can be cancer.
- A sample of tissue is taken and examined with a microscope and is oftentimes required to make a diagnosis of cancer.
In order to determine the best treatment, the doctor must know the stage of cancer, which is based on the size of the tumor and whether the cancer has spread to lymph nodes or other parts of the body. Doctors will often consider the patient’s age and general health when discussing treatment options. The goal of cancer treatment is to cure the cancer. However, in some cases the goal may be to control the disease or to reduce the symptoms for as long as possible.
Treatment plans often can include surgery, radiation therapy or chemotherapy. Hormone or biological therapy can also be considered for some patients. In addition, stem cell transplantation may be required so patients can receive high doses of chemotherapy or radiation therapy. There are some cancers that can respond to a single therapy, while others may respond to a combination of treatments.
A doctor may often prescribe treatments that work in a specific area or throughout the body. Local therapy works in a specific area to remove or destroy cancer in just one part of the body and is often done by surgery or radiation. Systemic therapy works throughout the body by sending drugs through the bloodstream to destroy cancer cells all over the body. Examples of systemic therapy include chemotherapy, hormone therapy and biologic therapy.
Since cancer treatments often damage healthy cells and tissues, side effects are common. The type of side effects can often depend on the type and extent of treatment and can be different for each person. In addition, side effects may change from one treatment session to the next. It is important, however, that treatment is never stopped without first speaking to a doctor or pharmacist, since some of the side effects can be managed.
- Since chemotherapy can affect all cells in the body, when the drug damages blood cells, a person may be more likely to get infections, bruise or bleed easily and to feel weak and tired. In addition, cells in hair roots can be affected and a person may suffer hair loss. The hair will grow back, but may be a different color or texture. Cells that line the digestive tract may be affected, which may often cause poor appetite, nausea, vomiting, diarrhea or mouth and lip sores.
- Hormone therapy
- Common side effects of hormone therapy may include weight gain, hot flashes, nausea and changes in fertility. For women, menstrual periods may stop or become irregular. Men may experience impotence, loss of sexual desire and breast growth or tenderness.
- Biological therapy
- This type of therapy helps the immune system fight cancer and is often given through a vein. Some people get a rash where the therapy is injected. Other side effects may include flu-like symptoms such as fever, chills, headache, muscle aches, fatigue, weakness and nausea.
There are many resources and organizations available to help, providing support, advocacy and information:
Centers for Disease Control and Prevention. http://www.cdc.gov/cancer. Accessed November 30, 2011.
National Institutes of Health. NCI. Handout on What You Need to Know About Cancer. NIH Publication No. 06-1566. July 2006.
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