How is cancer diagnosed?

If you have a sign or symptom that might mean cancer, the doctor will do a physical exam and ask about your medical history. In addition, the doctor usually orders various tests and exams. These may include imaging procedures, which produce pictures of areas inside the body, endoscopy, which allows the doctor to look directly inside certain organs, and laboratory tests. In most cases, the doctor also orders a biopsy, a procedure in which a sample of tissue is removed. A pathologist examines the tissue under a microscope to check for cancer cells.ImagingImages of areas inside the body help the doctor tell whether a tumor is present. These images can be made in several ways. In many cases, the doctor uses a special dye so that certain organs show up better on film. The dye may be swallowed or put into the body through a needle or a tube.X-rays are the most common way doctors made pictures of the inside of the body. In a special kind of x-ray imaging, a CT or CAT scan uses a computer linked to an x-ray machine to make a series of detailed pictures.In radionuclide scanning, the patient swallows or is given an injection of a mildly radioactive substance. A machine (scanner) measures radioactivity levels in certain organs and prints a picture on paper or films. By looking at the amount of radioactivity in the organs, the doctor can find abnormal areas.Ultrasonography is another procedure for viewing the inside of 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, 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.EndoscopyEndoscopy allows the doctor to look into the body through a thin, lighted tube called an endoscope. The exam is named for the organ involved (for example, colonoscopy to look inside the colon). During the exam, the doctor may collect tissue or cells for closer examination.Laboratory TestsAlthough no single test can be used to diagnose cancer, laboratory tests such as blood and urine tests give the doctor important information. If cancer is present, the lab work can show the effects of the disease on the body. In some cases, special tests are used to measure the amount of certain substances in the blood, urine, and other body fluids, or tumor tissue. The levels of these substances may become abnormal when certain kinds of cancer are present.BiopsyThe physical exam, imaging, endoscopy, and lab tests can show that something abnormal is present, but a biopsy is the only sure way to know whether the problem is cancer. In a biopsy, the doctor removes a sample of tissue from the abnormal area or may remove the whole tumor. A pathologist examines the tissue under a microscope. If cancer is present, the pathologist can usually tell what kind of cancer it is and may be able to judge whether the cells are likely to grow slowly or quickly. StagingWhen cancer is found, the patient's doctor needs to know the stage, or extent, of the disease to plan the best treatment. The doctor may order various tests and exams to find out whether the cancer has spread and, if so, what parts of the body are affected. In some cases, lymph nodes near the tumor are removed and checked for cancer cells. If cancer cells are found in the lymph nodes, it may mean that the cancer has spread to other organs.