Diagnosing Cancer

How a Diagnosis is Made
There are several ways to determine a diagnosis and measure the extent of disease.

Laboratory Tests

Blood and urine tests can give the doctor important information about a person's health. In some cases, special tests are used to measure the amount of certain substances, called tumor markers, in the blood, urine, or certain tissues. Tumor marker levels may be abnormal if certain types of cancer are present. However, lab tests alone cannot be used to diagnose cancer.


Images (pictures) of areas inside the body help the doctor see whether a tumor is present. These pictures can be made in several ways. X-rays are the most common way to view organs and bones inside the body.  A computed tomography (CT or CAT) scan is a special kind of imaging that uses a computer linked to an x-ray machine to make a series of pictures.

In radionuclide scanning, the patient swallows or receives an injection of a radioactive substance. A machine (scanner) measures radioactivity levels in certain organs and prints a picture on paper or film. The doctor can detect abnormal areas by looking at the amount of radioactivity in the organs. The patient's body quickly eliminates the radioactive substance after the test is done.

Ultrasonography is another procedure for viewing areas inside the body. High-frequency sound waves that cannot be heard by humans enter the body and bounce back. Their echoes produce a picture called a sonogram. These pictures are shown on a monitor like a TV screen and can be printed on paper.

In MRI (magnetic resonance imaging), a powerful magnet linked to a computer is used to make detailed pictures of areas in the body. These pictures are viewed on a monitor and can also be printed.


A biopsy is almost always necessary to help the doctor make a diagnosis of cancer. In a biopsy, tissue is removed for examination under a microscope by a pathologist. Tissue may be removed in three ways: endoscopy, needle biopsy, or surgical biopsy.

During an endoscopy, the doctor can look at areas inside the body through a thin, lighted tube.

  • Endoscopy allows the doctor to see what's going on inside the body, take pictures, and remove tissue or cells for examination, if necessary.
  • In a needle biopsy, the doctor takes a small tissue sample by inserting a needle into the abnormal (suspicious) area.
  • A surgical biopsy may be excisional or incisional. In an excisional biopsy, the surgeon removes the entire tumor, often with some surrounding normal tissue. In an incisional biopsy, the doctor removes just a portion of the tumor. If cancer is determined to be present, the entire tumor may then be removed immediately, or during another operation.


When cancer is diagnosed, the doctor will want to learn the stage, or extent, of the disease. Staging is a careful attempt to find out whether the cancer has spread and, if so, to which parts of the body. Treatment decisions depend on the results of staging. The doctor may order more laboratory tests, imaging studies, and/or additional biopsies to find out whether the cancer has spread.


Cancer patients frequently ask their doctor for statistics, or search on their own to answer the question, "What is my prognosis?"

Prognosis is a prediction of the future course and outcome of a disease, and an indication of the likelihood of recovery from that disease. However, it is only a prediction. When doctors discuss a patient's prognosis, they are attempting to project what is likely to occur for that individual patient.

A cancer patient's prognosis can be affected by many factors, particularly the type of cancer, the stage of the disease, and its grade (how closely the cancer resembles normal tissue and how fast the cancer is likely to grow and spread). Other factors that may also affect the prognosis include the patient's age, general health, and response to treatment. As these factors change over time, a patient's prognosis is also likely to change.

Seeking information about prognosis and statistics can help some people reduce their fears. How much information to seek and how to deal with it are personal decisions and matters. The doctor who is most familiar with a person's situation is in the best position to help interpret statistics and discuss prognosis. But even the doctor may not be able to describe exactly what to expect. 

Department of Radiation Oncology | 535 Barnhill Drive, RT 041 | Indianapolis, IN 46202-5289 | Phone: 317-944-2524 | FAX: 317-944-2486