How Do You Know if Your Thyroid Cancer Has Spread?

After you learn that you have thyroid cancer, you will likely immediately begin to wonder if your thyroid cancer has spread. When a cancer spreads, doctors call that a metastasis. This article will discuss how you can tell if your thyroid cancer has metastasized.

First, your doctor should be able to estimate your risk of metastasis based on the size and type of thyroid cancer that you have. Smaller cancers are less likely to have spread. Interestingly, thyroid cancers begin to spread quite early, with one study noting that more than 50% of patients with a 1cm papillary thyroid cancer already have cancer spread to their lymph nodes. If your cancer is bigger, the risks are higher because there are more cells that could spread. With some types of cancer, your doctor can also predict the risk based on labs (such as calcitonin or CEA if you have medullary thyroid cancer, or MTC).

Second, your doctor will want to confirm their suspicions with a sonogram. Why an ultrasound? It is excellent for the neck. It is cheap. It does not have radiation. And it is readily available. In fact, it's almost the ideal test. The only hard part about thyroid ultrasound for lymph nodes is that the experience of the person doing the exam is very important. If your doc doesn't do much ultrasound, they are less likely to know what they are looking for, or where to look, when they look for lymph nodes. It's one reason why your surgeon should do their own ultrasound!!

You might ask about other tests that could tell you if your thyroid cancer has spread, like a CT, MRI or a PET scan which is often used to tell if other cancers have spread. Each of those tests has limitations. CT scans use radiation, which has some (low) risks. We use it in case of known or suspected cancer spread, but not usually for low risk cancers. MRI is less detailed than CT, but it's good when we are worried about invasion into your spine, nerves, or voice box. And PET scans are really good if we know that you have aggressive cancer that is spreading... but actually don't work great for low risk cancers at all.

Once your doc has done the ultrasound to see if your thyroid cancer has spread, what do they do if they find something abnormal? First, they will usually recommend a similar biopsy (called an FNA) as you had in the first place on your thyroid. This can be done easily. Sadly, it can often come back inconclusive. In that case, we can add another test, known as thyroglobulin testing in the needle washout, that is very sensitive for identifying thyroid cancer. Unfortunately, many doctors don't know that you should use it if they are worried about thyroid cancer.

What should you NOT do when you suspect metastatic thyroid cancer? Don't have surgery to remove a lymph node (called an open biopsy) just to find out! This is a very inappropriate way to diagnose a neck cancer in most cases. Why? Because it will complicate the next surgery that you will need, which is to remove the lymph nodes and thyroid. You will have scar tissue from the open biopsy. Just don't do it. Now, there are always exceptions, but this should not be happening in 2025 (or whenever you are reading this!) If your doctor recommends this, please get a second opinion to confirm why it is being done.

With thyroid cancer, you want to have ONE surgery. The more surgeries you have as a patient, the lower your chances of cure become (there may be an exception when deciding to remove half or all of your thyroid, but that's about the only exception I can think of).

TL;DR

If you have thyroid cancer, an ultrasound is the test of choice to see if your thyroid cancer has spread.

If they find something suspicious, do a fine needle aspiration biopsy. Don't have a surgery just to remove a single lymph node!

Do have a thorough first surgery and consider removing nodes if you know you have cancer. While thyroid cancer doesn't usually kill people, it does like to come back. Find an experienced surgeon so that you have the best chance of cure!

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