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