Thyroid Cancer Diagnosis

Getting an accurate diagnosis is the first step in successful thyroid cancer treatment. At MD Anderson’s Endocrine Center, our experts are among the most experienced and skilled in recognizing, staging and treating thyroid cancer.

Most cases of thyroid cancer are found by chance during routine medical imaging. If an image shows a growth on the thyroid your doctor will conduct a thorough exam. This involves asking questions about your symptoms, overall health and your family’s medical history. If anyone in your family has had thyroid cancer, parathyroid disease or adrenal tumors, be sure to tell your doctor.

One or more of the following tests may be used to find out if you have cancer and if it has spread. These tests may also be used to find out if treatment is working.

Imaging exams: Imaging exams allow doctors to look inside the body for cancerous growths. Ultrasound is the most common exam used to help diagnose thyroid cancer. Other imaging techniques, such as CT and PET scans, may be used after a diagnosis to determine the extent of the disease. These additional exams are usually ordered when an aggressive form of thyroid cancer has been found.

Biopsy: During a biopsy, a small tissue sample is removed and examined under a microscope for cancer cells. This is the only way to definitively diagnose thyroid cancer. Doctors may order a biopsy when an initial imaging exam shows a growth on the thyroid, called a nodule.

Thyroid biopsies are performed by a radiologist using ultrasound to guide a needle to the thyroid nodule. The patient receives local anesthesia. Only around 12% of thyroid nodules that are biopsied are cancer. The rest are benign (not cancerous) growths.

Radioactive iodine thyroid scan: In the case of well differentiated thyroid cancer, a radioactive iodine thyroid scan may be used after thyroid surgery. This helps determine if any cancer remains or has spread to other parts of the body. During this procedure, the patient takes a liquid form of radioactive iodine (usually contained in several capsules). Since thyroid cells absorb iodine, they can then be identified using a scanner similar to a Geiger counter. Neither medullary thyroid cancer nor anaplastic thyroid cancer absorbs iodine, so this test is not useful for those diseases.

Blood tests: When thyroid cancer is suspected, doctors typically test the hormones related to thyroid function. This can help them understand the nature of the suspected cancer, the health of the thyroid gland itself and the effects of future treatment. The thyroid gland’s ability to function properly is not necessarily impacted by the presence of thyroid cancer, though. People with thyroid cancer usually have a normally functioning thyroid. Most people with abnormally functioning thyroid glands do not have thyroid cancer.

Genetic testing: People with medullary thyroid cancer should undergo a blood test to determine if they carry a genetic mutation that causes the hereditary form of the disease. If the test is positive, the patient’s children, siblings and parents may also have the mutation. They should be tested, too. More than 90% of people who have the genetic mutation will eventually develop the hereditary form of medullary thyroid cancer.

If a child has the gene, doctors often suggest removing the thyroid. Although children rarely develop MTC before age five, one type of hereditary MTC can occur within the first year of life. Doctors will help determine the best time for surgery. If the thyroid is removed, that person will need to take thyroid medication daily for the rest of his or her life.

Genetic testing of the tumor and blood can also be used to identify treatment options, including clinical trials, for patients with aggressive thyroid cancers. These include medullary thyroid cancer, poorly differentiated thyroid cancer and anaplastic thyroid cancer.