How Cancer Is Diagnosed
If you have a symptom or your screening test result suggests cancer, the doctor must find out whether it is due to cancer or some other cause. The doctor may ask about your personal and family medical history and do a physical exam. The doctor also may order lab tests, scans, or other tests or procedures.
High or low levels of certain substances in your body can be a sign of cancer. So, lab tests of the blood, urine, or other body fluids that measure these substances can help doctors make a diagnosis. However, abnormal lab results are not a sure sign of cancer. Lab tests are an important tool, but doctors cannot rely on them alone to diagnose cancer.
Imaging procedures create pictures of areas inside your body that help the doctor see whether a tumor is present. These pictures can be made in several ways:
- CT Scan:
An x-ray machine linked to a computer takes a series of detailed pictures of your organs. You may receive a dye or other contrast material to highlight areas inside the body. Contrast material helps make these pictures easier to read.
- Nuclear scan:
For this scan, you receive an injection of a small amount of radioactive material, which is sometimes called a tracer. It flows through your bloodstream and collects in certain bones or organs. A machine called a scanner detects and measures the radioactivity. The scanner creates pictures of bones or organs on a computer screen or on film. Your body gets rid of the radioactive substance quickly. This type of scan may also be called radionuclide scan.
An ultrasound device sends out sound waves that people cannot hear. The waves bounce off tissues inside your body like an echo. A computer uses these echoes to create a picture of areas inside your body. This picture is called a sonogram.
A strong magnet linked to a computer is used to make detailed pictures of areas in your body. Your doctor can view these pictures on a monitor and print them on film.
- PET scan:
For this scan, you receive an injection of a tracer. Then, a machine makes 3-D pictures that show where the tracer collects in the body. These scans show how organs and tissues are working.
X-rays use low doses of radiation to create pictures of the inside of your body.
In most cases, doctors need to do a biopsy to make a diagnosis of cancer. A biopsy is a procedure in which the doctor removes a sample of tissue. A pathologist then looks at the tissue under a microscope to see if it is cancer. The sample may be removed in several ways:
- With a needle: The doctor uses a needle to withdraw tissue or fluid.
- With an endoscope: The doctor looks at areas inside the body using a thin, lighted tube called an endoscope. The scope is inserted through a natural opening, such as the mouth. Then, the doctor uses a special tool to remove tissue or cells through the tube.
- With surgery: Surgery may be excisional or incisional.
- In an excisional biopsy, the surgeon removes the entire tumor. Often some of the normal tissue around the tumor also is removed.
- In an incisional biopsy, the surgeon removes just part of the tumor.