Diagnosis

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. Your doctor will likely ask you to swallow while he or she examines your thyroid because a nodule in your thyroid gland will usually move up and down during swallowing.

  Your doctor will also look for signs and symptoms of hyperthyroidism, such as tremor, overly active reflexes, and a rapid or irregular heartbeat. He or she will also check for signs and symptoms of hypothyroidism, such as a slow heartbeat, dry skin and facial swelling.

• Thyroid function tests. Tests that measure blood levels of thyroid-stimulating hormone (TSH) and hormones produced by your thyroid gland can indicate whether you have hyperthyroidism or hypothyroidism.
• Ultrasound. This imaging technique uses high-frequency sound waves to produce images of your thyroid gland. A thyroid ultrasound provides the best information about the shape and structure of nodules. Doctors may use it to distinguish cysts from solid nodules or to determine if multiple nodules are present. Doctors may also use it as a guide in performing a fine-needle aspiration biopsy.

• Fine-needle aspiration biopsy. Nodules are often biopsied to make sure no cancer is present. During the procedure, your doctor inserts a very thin needle in the nodule and removes a sample of cells.

  The procedure is usually done 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. Your doctor then sends the samples to a laboratory to have them analyzed under a microscope.

• Thyroid scan. 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. Hot nodules are almost always noncancerous.

  In some cases, nodules that take up less of the isotope — called cold nodules — are cancerous. However, a thyroid scan can't distinguish between cold nodules that are cancerous and those that aren't cancerous.