A tumor is an abnormal growth of body tissue. Tumors can be cancerous (malignant) or noncancerous (benign).
In general, tumors occur when cells divide and grow excessively in the body. Normally, the body controls cell growth and division. New cells are created to replace older ones or to perform new functions. Cells that are damaged or no longer needed die to make room for healthy replacements.
If the balance of cell growth and death is disturbed, a tumor may form.
Problems with the body's immune system can lead to tumors. Tobacco causes more deaths from cancer than any other environmental substance. Other risk factors for cancer include:
- Benzene and other chemicals and toxins
- Drinking too much alcohol
- Environmental toxins, such as certain poisonous mushrooms and a type of poison that can grow on peanut plants (aflatoxins)
- Excessive sunlight exposure
- Genetic problems
- Radiation exposure
Types of tumors known to be caused by viruses are:
- Cervical cancer (human papillomavirus)
- Hepatocellular carcinoma (hepatitis B and hepatitis C viruses)
Some tumors are more common in one gender than the other. Some are more common among children or the elderly. Others are related to diet, environment, and family history.
Symptoms depend on the type and location of the tumor. For example, lung tumors may cause coughing, shortness of breath, or chest pain. Tumors of the colon can cause weight loss, diarrhea, constipation, iron deficiency anemia, and blood in the stool.
Some tumors may not cause any symptoms. Others, such as pancreatic cancer, do not usually cause symptoms until the disease has reached an advanced stage.
The following symptoms may occur with tumors:
Exams and Tests
Your doctor or nurse might see a tumor, such as skin cancer. But most cancers cannot be seen during an exam because they are deep inside the body.
When a tumor is found, a piece of the tissue is removed and examined under a microscope. This is called a biopsy. It is done to determine if the tumor is noncancerous (benign) or cancerous (malignant). Depending on the location of the tumor, the biopsy may be a simple procedure or a serious operation.
Other tests that may be done include:
- Blood tests
- Bone marrow biopsy (most often for lymphoma or leukemia)
- Chest x-ray
- Complete blood count (CBC)
- Liver function tests
Treatment varies based on:
- Type of tumor
- Whether it is cancer
- Location of the tumor
You may not need treatment if the tumor is:
- Noncancerous (benign)
- In a "safe" area where it will not cause symptoms or problems with the way an organ works
Sometimes benign tumors may be removed for cosmetic reasons. Benign tumors of the brain may be removed because of their location or harmful effect on the surrounding normal brain tissue.
If a tumor is cancer, possible treatments may include:
- Targeted cancer therapy
- Biologic therapy
- Other treatment options
A cancer diagnosis often causes a lot of anxiety and can affect a person's entire life. There are many resources for cancer patients.
The outlook varies greatly for different types of tumors. If the tumor is benign, the outlook is generally very good. But a benign tumor can cause severe problems, such as in the brain.
If the tumor is cancerous, the outcome depends on the type and stage of the tumor at diagnosis. Some cancers can be cured. Some that are not curable can still be treated, and people can live for many years with the cancer. Still other tumors are quickly life threatening.
Moscow JA, Cowan KH. Biology of cancer. In Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 185.
Review Date: 8/17/2014
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, and the A.D.A.M. Editorial team.