Diagnosing Cancer

How is cancer diagnosed?

Certain tests are needed to determine whether a person has cancer, or if another condition (such as an infection) is imitating the symptoms of cancer. Sometimes, it is necessary to repeat testing if the person's condition changes, if a sample collected was not of good quality, or an abnormal test result needs to be confirmed. The correct diagnosis is needed to guide treatment. In addition to a complete medical history and physical exam, diagnostic procedures for cancer may include one, or more of, the following:

  • Complete blood count (CBC). This blood test is a measurement of size, number, and maturity of different blood cells in a specific volume of blood. Abnormal cells may indicate cancer. Variation in the normal number, size, and maturity of cells may indicate a problem.

  • Bone marrow aspiration, biopsy, or both. This procedure involves taking a small amount of bone marrow fluid (aspiration) and/or solid bone marrow tissue (called a core biopsy), usually from the back of the hip bones, to be examined for the number, size, and maturity of blood cells and/or abnormal cells.

  • Spinal tap (lumbar puncture). This procedure evaluates the fluid around the spine and brain for pressure and/or infection, and finds any abnormal cells. A special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problem. CSF is the fluid that bathes the brain and spinal cord.

  • Lymphangiogram (LAG). This is an imaging study that can detect cancer cells or abnormalities in the lymphatic system and structures. A dye is injected into the lymph system.

  • Ultrasound (sonography). This is a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels. Tumors in the stomach, liver, and kidneys can often be seen with an ultrasound.

  • Biopsy of the tumor. A biopsy is a procedure in which a sample of tissue is removed from the tumor and examined under a microscope. Biopsies are necessary for a diagnosis, since it gives the most accurate analysis of tissue. 

  • Bone scans. Pictures or X-rays are taken of the bone after a radioactive dye has been injected that is absorbed by bone tissue. These scans are used to find tumors and bone abnormalities.

  • X-rays. These tests use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film. X-rays may be taken of any part of the body to detect a tumor (or cancer).

  • CT scan. This is an imaging test that uses X-rays and a computer to make detailed images of the body. A CT scan shows details of the bones, muscles, fat, and organs.

  • Positron emission tomography and CT scans (PET-CT). CT scan provides detailed pictures of tissues and organs while the PET scan reveals any abnormal activity. A more complete image is provided by combining these tests. 

  • MRI. An MRI uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. This test is done without the use of X-rays. 

  • Blood tests. Blood tests are used to evaluate electrolytes, liver function, kidney function, presence of infection, tumor markers (chemicals released by a tumor), and/or genetic testing. Genetic counseling may be recommended to families that are found or suspected to have an inherited predisposition to developing cancer, in order to identify other family members who may be at increased risk.

  • Surgery. Surgery may be needed to do a biopsy, remove tumors, remove entire organs affected by disease, and to look for tumors that may not be found with diagnostic imaging.