ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. To see other pages, use the menu.
Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the cancer has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.
For most types of cancer, a biopsy is the only sure way for the doctor to know whether an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.
This list describes options for diagnosing this type of cancer, and not all tests listed will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:
The type of cancer suspected
Your signs and symptoms
Your age and medical condition
The results of earlier medical tests
In addition to a physical examination, the following tests may be used to diagnose thymoma or thymic carcinoma:
Computed tomography (CT or CAT) scan. A CT scan  creates a 3-dimensional picture of the inside of the body using x-rays taken from different angles. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. A CT scan can also be used to measure the tumor’s size. A CT scan of the chest is the most common test used to look for and evaluate thymoma. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill to swallow. An MRI and PET may provide more information but are not always needed (see below).
Magnetic resonance imaging (MRI). An MRI  uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can also be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill to swallow.
Positron emission tomography (PET) scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan . However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.
Biopsy and Chamberlain procedure. A biopsy  is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. A biopsy is not usually the first test done for thymoma. Usually a person will first have imaging tests (see above), such as CT, MRI, or PET scan.
The type of biopsy performed will depend on the location of the cancer. A needle biopsy is the use of a thin needle that is inserted into the tumor to remove a piece of tissue. Depending on the location of the tumor, surgery may be needed to get enough tissue to make a diagnosis. Also known as the Chamberlain procedure, this type of surgery is performed by making a 2-inch cut next to the breastbone and removing a sample of the tumor.
After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer; this is called staging.
The next section in this guide is Stages . It explains the system doctors use to describe the extent of the disease. Or, use the menu to choose another section to continue reading this guide.