A tumor is an abnormal growth of body tissue. Tumors can be cancerous (malignant) or non-cancerous (benign).

In general, tumors appear to occur when there is a problem with the dividing of cells in the body. Typically, the division of cells in the body is strictly controlled. 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 division 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 causes include obesity, inactivity (sedentary lifestyle), excessive alcohol consumption, radiation, genetic problems, excessive sunlight exposure, benzene, and a number of other chemicals and toxins.

Certain viruses can play a role in the development of tumors, such as cervical cancer and hepatocellular carcinoma.

Some tumors are more common in one sex than the other, some are more common among children or the elderly, and some vary with diet, environment, and your 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, while tumors of the colon can cause weight loss, diarrhea, constipation, iron deficiency anemia, and blood in the stool. Some tumors produce no symptoms, but symptoms that often accompany tumors include:

• Fever
• Chills
• Night sweats
• Weight loss
• Loss of appetite
• Fatigue
• Malaise

Like the symptoms, the signs of tumors vary based on their site and type. When a tumor is found, a biopsy is performed to determine if the tumor is benign or malignant. Depending on the location of the tumor, the biopsy may be a simple procedure or a serious operation. Most patients with tumors undergo CT scans or MRI to determine the exact location of the tumor and its extent. More recently, positron emission tomography (PET) scans have been used to visualize certain tumors types.

Common tests to most patients with tumors include:

• CT scan
• MRI
• PET scan
• Complete blood count (CBC)
• Blood chemistries
• Biopsy of the tumor
• Bone marrow biopsy (most often for lymphoma or leukemia)
• Chest x-ray

Treatment also varies based on the type of tumor, whether it is benign or malignant, and its location. If the tumor is benign (meaning it has no potential to spread) and is located in a "safe" area where it will not cause symptoms or disturb the proper functioning of the organ, sometimes no treatment is needed. Sometimes benign tumors may be removed for cosmetic reasons, however. 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 malignant, treatments include surgery, radiation, chemotherapy, or a combination of these methods.

If the cancer is confined to one location, the goal of treatment is usually surgical removal of the tumor and cure. If the tumor has spread to local lymph nodes only, sometimes these can also be removed. If all of the cancer cannot be removed with surgery, the options for treatment include radiation and chemotherapy, or both. Some patients require a combination of surgery, radiation and chemotherapy.

In contrast, lymphoma is rarely treated with surgery. Chemotherapy and radiation therapy are most often used for treating lymphoma.

The diagnosis of cancer often causes a lot of anxiety and can affect one's entire life. There are numerous resources for cancer patients, see cancer resources.

The outlook varies widely among different types of tumor. If the tumor is benign, the prognosis is generally very good. However, there are some instances where a benign tumor can cause significant problems, for instance, in the brain.

If the tumor is malignant, the outcome varies depending on the stage of the tumor at diagnosis. Some cancers can be cured. Some that are not curable can still be treated and patients can live for many years with the cancer. Still other tumors are rapidly fatal.

Complications can occur if a tumor is located in a region of the body where it compromises the function of the normal organ. If the tumor is malignant, it can also cause complications if it spreads or metastasizes.

Call your healthcare provider if you notice any suspicious lumps or bumps on your body or if you notice a new or changing mole on your skin.

The risk of malignant tumors (cancer) can be reduced by not smoking or chewing tobacco, avoiding heavy alcohol consumption, eating a healthy diet, exercising regularly, maintaining a healthy weight, reducing sun exposure if you burn easily, and minimizing exposure to radiation and toxic chemicals.