Tests and diagnosis

By Mayo Clinic Staff

In assessing a lump or nodule in your neck, one of your doctor's main goals is to rule out the possibility of cancer. But your doctor will also want to know if your thyroid is functioning properly. Tests include:

  • Physical exam. You'll likely be asked to swallow while your doctor examines your thyroid because a nodule in the thyroid gland will usually move up and down during swallowing.
  • Thyroid function tests. Tests that measure blood levels of thyroxine and triiodothyronine, hormones produced by your thyroid gland, and thyroid-stimulating hormone (TSH), which is released by your pituitary gland, can indicate whether your thyroid is producing too much thyroxine (hyperthyroidism) or too little (hypothyroidism).
  • Ultrasonography. This imaging technique uses high-frequency sound waves rather than radiation to produce images. It provides the best information about the shape and structure of nodules and may be used to distinguish cysts from solid nodules, to determine if multiple nodules are present and as a guide in performing a fine-needle aspiration biopsy.
  • Fine-needle aspiration (FNA) biopsy. Nodules are often biopsied to make sure no cancer is present. FNA biopsy helps to distinguish between benign and malignant thyroid nodules. During the procedure, your doctor inserts a very thin needle in the nodule and removes a sample of cells. The procedure, which is carried out in your doctor's office, takes about 20 minutes and has few risks. Often, your doctor will use ultrasound to help guide the placement of the needle. The samples are then sent to a laboratory and analyzed under a microscope.
  • Thyroid scan. In some cases, your doctor may recommend a thyroid scan to help evaluate thyroid nodules. During this test, an isotope of radioactive iodine is injected into a vein in your arm. You then lie on a table while a special camera produces an image of your thyroid on a computer screen.

    Nodules that produce excess thyroid hormone — called hot nodules — show up on the scan because they take up more of the isotope than normal thyroid tissue does. Cold nodules are nonfunctioning and appear as defects or holes in the scan. Hot nodules are almost always noncancerous, but a few cold nodules are cancerous. The disadvantage of a thyroid scan is that it can't distinguish between benign and malignant cold nodules.

    The length of a thyroid scan varies, depending on how long it takes the isotope to reach your thyroid gland. You may have some neck discomfort because your neck is stretched back during the scan, and you'll be exposed to a small amount of radiation.

Apr. 04, 2014