Diagnosis

Doctors use many tests to diagnose cancer and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of cancer suspected
  
  
• Severity of symptoms
  
  
• Previous test results

The following tests may be used to diagnose thyroid cancer:

Physical examination. The doctor will feel the neck, thyroid, throat, and lymph nodes (the tiny, bean-shaped organs that help fight infection) in the neck for unusual growths or swelling. If surgery is recommended, the larynx may be examined at the same time with a laryngoscope (thin, flexible tube with a light).

Blood tests. The doctor may use a blood test to check the level of thyroid-stimulating hormone (TSH). A measurement of thyroid hormone levels and antithyroid antibodies may be done as well. If MTC is a possibility, the doctor will order a test to check for high calcitonin levels and a blood test to detect the presence of RET proto-oncogenes (see Risk Factors). The search for RET proto-oncogenes is often recommended if there is a family history of MTC.

Ultrasound. An ultrasound uses sound waves to create a picture of the internal organs. An ultrasound wand or probe is guided over the skin of the neck area. High-frequency sound waves create a pattern of echoes that show the doctor the thyroid gland size and specific information about any nodules, including whether they are solid or cysts (fluid-filled sacs).

Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. The way to determine whether a nodule is malignant or benign is through a biopsy. During this procedure, the doctor removes cells from the nodule that are then examined by a cytopathologist (a doctor who specializes in analyzing cells and tissue) to determine if cancer is present. A biopsy for thyroid nodules will be done one of two ways:

• Fine needle aspiration. This procedure is usually performed in a doctor’s office or clinic. It is an important diagnostic step to determine if a thyroid nodule is benign or malignant. A local anesthetic may be injected into the skin to numb the area before the biopsy. The doctor inserts a thin needle into the nodule and removes cells and some fluid. The procedure may be repeated two or three times to obtain samples from different areas of the nodule. The report done by the pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease) can be positive (meaning there are cancerous cells), negative (meaning there are no cancerous cells), or undetermined.
  
  
• Surgical biopsy. If the needle aspiration biopsy is not clear, the doctor may suggest a biopsy in which the nodule and possibly the affected lobe of the thyroid will be removed. This procedure is usually done under general anesthesia and on an inpatient or outpatient basis.

Radionuclide scanning. This test, also called a full-body scan or a radioactive iodine (I-131 or RAI) scan, is used most often to learn more about a thyroid nodule. In this test, the patient swallows a small, harmless amount of radioactive iodine, which allows the doctor to see differences between thyroid cells and other body structures.

Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images.

Learn more about what to expect when having common tests, procedures, and scans.

Find out more about common terms used during a diagnosis of cancer.