Thyroid Cancer Overview

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Early Detection, Diagnosis, and Staging TOPICS

How is thyroid cancer found?

Many thyroid cancers can be found early. Some early thyroid cancers are found when patients see their doctors because of neck lumps or bumps they have noticed. If you have symptoms such as a lump or swelling in your neck, you should see your doctor right away.

Many thyroid cancers are found by the doctor during a routine checkup or when people have imaging tests (such as ultrasound or CT scans of the neck) for other health problems.

If you have any signs or symptoms that suggest you might have thyroid cancer, your doctor will take your history, examine you, and then order more tests.

Medical history and physical exam

Your doctor will take a medical history. You will be asked questions about your possible risk factors, symptoms, and any other health problems or concerns. If someone in your family has had thyroid cancer, tell your doctor, as you might be at high risk for this disease.

During the physical exam, your doctor will pay special attention to the size and firmness of your thyroid and any enlarged lymph nodes in your neck.

Imaging tests to look at the thyroid

If you have a lump in your thyroid, your doctor may order one or more of these tests


Ultrasound uses sound waves to create pictures of parts of your body. For this test, a small wand is placed on the skin in front of your thyroid gland. It gives off sound waves and picks up the echoes as they bounce off the thyroid. The echoes are seen as a black and white image on a computer screen. No radiation is used in this test.

This test can help show if thyroid nodules are solid or filled with fluid. (Solid ones are more likely to be cancer.) It can also be used to help guide a biopsy needle into a nodule to take a sample. Ultrasound can also help show whether any nearby lymph nodes are enlarged because the thyroid cancer has spread.

Radioiodine scan

Radioiodine scans can be used to help find out if someone with a lump in the neck might have thyroid cancer. They are also often used in patients with differentiated thyroid cancer to help show if it has spread. (Medullary thyroid cancer cells do not take up iodine, so radioiodine scans are not used for this cancer.)

For this test, a small amount of radioactive iodine is swallowed as a pill or put into a vein. Over time, the iodine is absorbed by the thyroid cells. A special camera is used several hours later to see the radioactivity.

For a thyroid scan, the camera is placed in front of your neck to measure the amount of radiation in the gland. Abnormal areas of the thyroid that have less radioactivity than the surrounding tissue are called cold nodules, and areas that take up more radiation are called hot nodules. Hot nodules usually are not cancer, but cold nodules can be either benign or cancer. So this test by itself can’t diagnose thyroid cancer.

After surgery for thyroid cancer, whole-body radioiodine scans are useful in looking to see if cancer has spread throughout the body.

Radioactive iodine can also be used to treat differentiated thyroid cancer, but it is given in much higher doses. This type of treatment is described in the section “Radioactive iodine treatment.”


If imaging tests such as ultrasound and a radioiodine scan suggest that you could have thyroid cancer, you will need a biopsy to know for certain. For a biopsy, a sample of cells from the area of concern are removed and looked at under a microscope.

The most common type of biopsy to look for thyroid cancer is called a fine needle aspiration (FNA) biopsy. For this, the doctor puts a thin, hollow needle into the lump to draw out cells and a few drops of fluid. This type of biopsy can usually be done in your doctor’s office or clinic. Before the biopsy, medicine may be used to numb the skin over the nodule. Sometimes ultrasound is used to help the doctor find the right place to put the needle.

Sometimes an FNA biopsy will need to be repeated because the samples didn’t contain enough cells. Most FNA biopsies will show that the thyroid nodule is benign. Only about 1 out of every 20 biopsies will clearly show cancer.

Sometimes the doctor can’t tell for certain that the cells are cancer just by how they look under the microscope and will need to do special tests to look for certain genes.

In some cases, another biopsy may be needed to get a better sample. This might include a biopsy using a larger needle or a surgical “open” biopsy to remove the nodule or a larger part of the thyroid gland. This kind of biopsy is done in the hospital while you are in a deep sleep.

Imaging tests to look for spread of thyroid cancer

Imaging tests make pictures of the inside of your body. They may be done for a number of reasons:

  • To find suspicious areas that might be cancer
  • To learn how far cancer may have spread
  • To help find out if treatment has been working

Chest x-ray

If you have thyroid cancer, your chest may be x-rayed to see if cancer has spread to your lungs.

Computed tomography (CT) scan

The CT scan is an x-ray test that gives detailed pictures of your body. The CT scan can help show the place and size of thyroid cancers and whether they have spread to nearby areas. A CT scan can also be used to look for spread into distant organs like the lungs.

A CT scanner has been described as a large donut, with a narrow table in the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.

Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures.

Before the test, you may be asked to drink a contrast solution or receive an IV (intravenous) line through which a different contrast dye is put in. This helps better outline structures in your body. You might feel some flushing (a feeling of warmth). Some people are allergic and get hives. Rarely, more serious problems like trouble breathing or low blood pressure can happen. Be sure to tell the doctor if you have any allergies or have ever had any problems from contrast dye used for x-rays.

In some cases, a CT scan can be used to guide a biopsy needle right into a suspected area of cancer spread.

Because the CT contrast dye contains iodine, (which can cause problems with radioiodine scans described above), many doctors prefer MRI scans instead of CT scans.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans can be used to look for cancer in the thyroid or cancer that has spread to other parts of the body. But ultrasound is usually the first choice for looking at the thyroid. MRI scans are helpful in looking at the brain and spinal cord.

MRI scans use radio waves and strong magnets instead of x-rays. A contrast material is often put into a vein before the scan to better show the details.

MRI scans take longer than CT scans — often up to an hour. And you might have to lie inside a narrow tube, which can upset people who don’t like enclosed spaces. Newer, more open MRI machines can sometimes be used instead. The machine also makes buzzing and clicking noises, so some centers provide earplugs to block it out.

PET (positron emission tomography) scan

For a PET scan, a kind of radioactive sugar is put into the blood. The amount used is very low. Because cancer cells in the body are growing quickly, they absorb more of the sugar than normal cells. After waiting about an hour, you lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body.

This test can be very useful if your thyroid cancer is one that doesn’t take up radioactive iodine. In this case, the PET scan may be able to tell whether the cancer has spread.

Some machines are able to do both a PET and CT scan at the same time. This lets the doctor see areas that “light up” on the PET scan in more detail.

Blood tests

Blood tests alone can’t tell if a person has thyroid cancer. But they can help show if the thyroid is working as it should, which may help the doctor decide what other tests may be needed.

Thyroid tests

Your blood may be tested for levels of thyroid hormones (T3 and T4), thyroid-stimulating hormone (TSH), and thyroglobulin to see if the thyroid is working normally.

These tests can’t tell if you have thyroid cancer, but they may be done during and after cancer treatment to check thyroid function or to help find out if the cancer may have returned.

Other blood tests

You may have other blood tests as well. If you are scheduled for surgery, tests will be done to check your blood cell counts, to look for bleeding problems, and to check your liver and kidney function.

Vocal cord exam

Thyroid tumors can sometimes affect the vocal cords. If you are going to have surgery to treat thyroid cancer, a vocal cord exam probably will be done ahead of time to see if the vocal cords are moving the way they should. For this exam, the doctor looks down the throat at the voice box with special mirrors or with a thin tube with a light and a lens on the end (a laryngoscope).

Last Medical Review: 02/27/2014
Last Revised: 02/13/2015