Thyroid Cancer: Diagnosis

Some thyroid tumors are discovered after the patient notices swelling or a small nodule on the front of the neck. Others are found incidentally, through imaging tests performed for other conditions.

Video

Doctors use ultrasound to determine whether a thyroid tumor is cancerous or noncancerous.

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In most cases, patients arrive at Memorial Sloan Kettering after receiving a diagnosis of thyroid cancer from a physician at another institution. Depending on the care you have already received, your doctor at Memorial Sloan Kettering may suggest additional tests to determine the specific characteristics of your tumor and to begin to develop a treatment plan. These tests may include:

Physical Examination

The first test for thyroid cancer is a physical examination. Your doctor will feel your thyroid, throat, and lymph nodes in the neck to look for unusual growths or swelling, which may indicate a thyroid tumor. Your doctor may also examine your vocal cords using a small scope inserted through your nose and into your throat.

Ultrasound

This imaging technique uses sound waves to evaluate thyroid nodules and lymph nodes in the neck. Ultrasound can be used to determine whether the appearance of a thyroid nodule is suspicious or benign. Further evaluation with a biopsy and other tests are used to make a diagnosis.

Biopsy

Doctors often remove a small amount of cells, fluid, or other tissue for examination under a microscope to determine whether a thyroid nodule is benign or malignant. Two types of biopsies are used to diagnose thyroid cancer:

  • Fine Needle Aspiration
    This type of biopsy may be performed in a doctor’s office or by a radiologist who uses ultrasound to guide the placement of a very fine needle into the nodule.
  • Surgical Biopsy
    Depending on the result of the needle aspiration, surgery may be required to remove part or all of the thyroid gland. This procedure is performed under general anesthesia in the hospital or on an outpatient basis.

Blood Tests

Your doctor may use a blood test to measure levels of thyroid-stimulating hormone (TSH), a substance made by the pituitary gland that controls the growth of follicular cells. Blood tests to measure calcitonin levels and detect the presence of mutations in the RET gene also may be performed if your doctor suspects medullary thyroid cancer. Siblings and children of patients with MTC are encouraged to seek genetic testing. For more information, visit Hereditary Cancer & Genetics.

Radioactive Iodine (RAI) Scan

RAI scans may be used to learn more about a thyroid nodule or to determine whether thyroid cancer has spread to other parts of the body. For this test, your doctor will ask you to swallow a liquid or capsule that contains a small amount of radioactive iodine, which is absorbed by the thyroid gland (or thyroid cancer cells anywhere in the body). Several hours later, a special camera is used to identify tissue that has absorbed the iodine.

Positron Emission Tomography (PET) Scan

PET imaging is sometimes used to find malignant tumor cells and determine whether the cancer has spread beyond the thyroid1. In addition, PET may be used to help assess a patient’s prognosis and response to treatment2. Before imaging, a small amount of radioactive sugar is injected into a vein. Cancer cells, which absorb sugar more rapidly than normal cells, are highlighted on the PET scan.

Octreotide (Somatostatin Receptor Scintigraphy) Scan

Medullary thyroid tumors often have several receptors for somatastatin - a substance that suppresses the hormones involved in growth, metabolism, and digestion. Patients suspected of having MTC receive an injection of octreotide, a synthetic form of somatostatin that is attached to a radioactive substance. Radiation-sensitive imaging tests reveal how much octreotide has been absorbed, indicating the presence and size of a tumor.

1S. Larson, R. Robbins. Positron emission tomography in thyroid cancer management. Semin Roentgenol. 2002 Apr;37(2):169-74. [PubMed abstract]

2R. Robbins, Q. Wan, R. Grewal, et al. Real-time prognosis for metastatic thyroid carcinoma based on 2-[18F0 fluoro-2-deoxy-D-glucose-positron emission tomography scanning. J Endocrinol Metab. 2006 Feb;91(2):498-505. [PubMed abstract]