If you have some of the symptoms of thyroid cancer, your doctor will begin your diagnosis with a medical history and physical exam.
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Medical history and physical examination - Your doctor will take a complete medical history by asking you about your risk factors, symptoms, and other health problems or concerns. Tell your doctor if someone in your family has had thyroid cancer (especially medullary thyroid cancer) or adrenal gland tumors (pheochromocytomas). The doctor will also do a physical exam to look for signs of thyroid cancer and other health problems. During your physical exam, your doctor will pay special attention to the size and firmness of your thyroid and any enlarged lymph nodes in your neck.
No blood test can tell whether a thyroid nodule is cancerous. But blood tests can provide some useful information.
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Thyroid stimulating hormone (TSH) - TSH controls the release of thyroid hormone and the growth of thyroid follicular cells. A blood test for TSH can provide information about the activity of your thyroid gland.
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Calcitonin - The calcitonin level of healthy people rises slightly after an injection of calcium, but it is much higher in people with medullary thyroid cancer (MTC). Your doctor might order a blood calcitonin test to show whether you could have MTC. The doctor will draw a small amount of blood before injecting you with calcium. The doctor will draw blood again at 2, 5, 10, and 15 minutes after the injection.
The only way to be sure whether you have thyroid cancer is by removing a small sample of tumor for examination under the microscope. The procedure to remove a tissue sample is called a biopsy. The biopsy might be done by fine needle aspiration or during surgery.
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Fine needle aspiration (FNA) - The doctor inserts a thin needle directly into the nodule for a few seconds and takes out cells and a few drops of fluid. The doctor might do the same procedure a few times in several different areas of the same nodule. A pathologist (a doctor who diagnoses diseases by examining tissue) will examine the cells under a microscope to see if they are cancerous. Sometimes the doctor will use an ultrasound machine during the biopsy to help guide the needle into small nodules.
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Surgical biopsy - If your doctor cannot make a diagnosis from the fine-needle aspiration, he or she may remove the nodule and possibly the affected lobe of the thyroid by surgery. A pathologist will then examine the tissue for cancer cells.
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Sentinel lymph node biopsy - The doctor injects a radioactive tracer and blue dye into the tumor. The dye and radioactive material travel to the lymph nodes where the cancer is most likely to spread. The surgeon then removes the "sentinel node,” which is the first lymph node into which a tumor drains and is also the one most likely to contain cancer cells. If the sentinel node is cancer-free, the doctor does not take out any more lymph nodes.
Imaging procedures allow doctors to learn where the cancer is located and whether it has spread from the thyroid to other areas of the body.
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Computed tomography (CT or CAT) scan - Instead of taking one picture, like a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer combines these pictures into an image of a slice of your body (like a loaf of sliced bread). CT scans can show tumors within a thyroid gland as well as the size of the tumor, whether it is growing into nearby tissues, and if it has spread to lymph nodes in the neck or distant structures. CT scans are not usually used to diagnose thyroid cancer. But they might be used to find out if a thyroid cancer has spread.
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Magnetic resonance imaging (MRI) - This procedure uses powerful magnets and radio waves to take detailed cross-sectional images. MRI produces images of cross-sectional slices of your body like a CT scanner; it can also produce images of slices that are parallel to the length of your body. MRI scans can show tumors within a thyroid gland as well as the size of the tumor, whether it is growing into nearby tissues, and if it has spread to lymph nodes in the neck or distant structures.
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Octreotide scan - Octreotide scans use a radioactively tagged hormone. This procedure is sometimes used to evaluate the spread of medullary thyroid cancer.
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Positron emission tomography (PET) - Cancer cells use glucose (sugar) more quickly than most other body organs. During a PET scan, the doctor injects a small amount of glucose that has a radioactive atom into your arm. A special camera in the PET machine can detect the radioactivity. This test is useful to see if the cancer has spread.
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Radioiodine thyroid scan (radionuclide scan) - You will take a small amount of radioactive iodine by mouth or it will be injected into a vein. Your body concentrates these radioactive chemicals in the thyroid gland, and a special camera placed in front of your neck measures the amount of radiation in the gland. Abnormal areas of the thyroid with less radioactivity than the surrounding tissue are called cold nodules, and nodules that take up more radiation—and are usually benign—are called hot nodules. Because benign and cancerous nodules can show up as cold nodules, this test is not usually very helpful in diagnosing thyroid cancer. However, once a biopsy has determined that you have thyroid cancer, these scans are very useful in finding out whether the cancer has spread to other parts of the body.
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Ultrasound - The doctor holds a transducer near your thyroid gland. The transducer sends high-frequency sound waves and detects echoes that bounce off thyroid tissue. Normal thyroid tissue and most thyroid nodules make different echo patterns. A computer processes these echo patterns to create a picture of the thyroid gland. This test can be used to check the number and size of thyroid nodules. However, thyroid cancers and most benign nodules look the same on ultrasound studies, so this test is not done routinely.
This content has been reviewed and approved by Myo Thant, MD.