What Is Thyroid Cancer?
Thyroid cancer is a type of cancer that starts in your thyroid gland. A gland is an organ in your body that makes a substance.
Your thyroid is shaped like a small butterfly and is found inside the lower front of your neck. It has two lobes, or pieces, one on either side of your windpipe, joined by a band of tissue called the isthmus.
Your thyroid controls your metabolism. It also makes and releases hormones that direct many functions in your body, including how you use energy, how you produce heat, and how you consume oxygen.
Thyroid cancer develops when abnormal cells change or mutate in the tissues of your thyroid gland. The abnormal (cancer) cells begin multiplying and, once there are enough of them, they form a tumor or mass in your thyroid.
If it’s caught early, thyroid cancer is one of the most treatable forms of cancer.
Types of Thyroid Cancer
Researchers have identified four main types:
Papillary thyroid cancer
If you have thyroid cancer, you probably have this type. It’s responsible for 80% of all thyroid cancer cases. It tends to grow slowly, but often spreads to the lymph nodes in your neck. Lymph nodes act like filters to rid your body of foreign matter like cancer cells and infections. They clean fluid that comes from body tissues before it moves through the lymphatic system, part of your immune system. Even if the cancer has spread to your lymph nodes, you have a very good chance of a full recovery.
Follicular thyroid cancer
This makes up between 10% and 15% of all thyroid cancers in the United States. It can spread into your lymph nodes and is also more likely to spread into your blood vessels. The chance of recovery, if you have this type, is good but slightly less than if you have papillary.
Medullary thyroid cancer
This makes up about 4% of all thyroid cancer cases. If you have this kind, it’s likely to be found at an early stage because it produces a hormone called calcitonin, which doctors keep an eye out for in blood test results.
Anaplastic thyroid cancer
This is usually the most severe type, because it’s aggressive in spreading to other parts of the body. It’s also rare (about 2% of thyroid cancer cases) and the hardest to treat.
Cancers are often described as well-differentiated or undifferentiated. Well-differentiated cancer cells have specialized structures and tend to grow and spread slowly. Papillary and follicular thyroid cancers are well-differentiated.
Undifferentiated cancers are the opposite. They don't have specialized structures and tend to grow and spread quickly. Medullary and anaplastic thyroid cancers are undifferentiated.
Thyroid cancer is rare. It made up just 2.2% of all new cancer cases in 2024.
Symptoms of Thyroid Cancer
In the beginning you may not notice any symptoms of thyroid cancer. But as it grows, you could notice any of the following problems:
- Neck or throat pain
- Lump in your neck
- Difficulty swallowing
- Vocal changes, hoarseness
- Cough
Many of these symptoms may be signs of conditions that aren't cancer, but you should still see a doctor to be sure. Most thyroid cancers are found early when people go to their doctors about a swelling in their neck.
Thyroid Cancer Stages
The staging system most often used is the AJCC (American Joint Committee on Cancer)TNM system. It is based on three pieces of information:
T (tumor). How large is the tumor? Has it invaded nearby tissues?
T0 means no evidence of a tumor. T1-T4 is a progression, with T4 indicating the largest and most invasive tumor.
N (nodes). Has the cancer spread to nearby lymph nodes?
N0 means the cancer hasn't spread to lymph nodes. N1-N3 is a progression for how far the cancer has spread, with N3 being the biggest spread.
M (metastasis). Has the cancer metastasized (spread) to distant organs, like the lungs or the liver?
M0 means the cancer hasn't spread to distant organs. M1 means there is evidence of spread to distant organs.
Within these categories, there are subsections. For instance, M1b means the cancer spread to 2 or more organs.
Your doctor determines your TNM categories from looking at test results (blood tests, X-rays, etc.) and from physically examining you. Once your TNM categories have been decided, the next step is your staging. Cancer stages run from I to IV. The lower the number, the less your cancer has spread. Here's a simplified version of thyroid cancer stages:
- Stage 0 - Cells that look like cancerous cells (precancerous) are spotted, but they're only where they were found (T0, N0, M0).
- Stage I - The tumor is small and in one area (T1-T2, N0, M0).
- Stage II - The tumor is larger and may have spread to lymph nodes (T1-T2, N1, M0).
- Stage III - The tumor has grown deeper into surrounding tissues and may have spread to lymph nodes (T1-T4, N2-N3, M0).
- Stage IV - The tumor has spread to other organs (metastatic cancer, T1-T4, N1-N3, M1).
Some doctors use a letter along with a stage. For instance, they might say your cancer is stage IIIA. The four letters are A, B, C and D. This tells you how fast-growing (aggressive) your cancer is. A is the least aggressive and D is the most aggressive.
Causes of Thyroid Cancer
Most people who get thyroid cancer get it through acquired gene mutation. This means the gene mutation happened randomly in their lifetime. For instance, half of all papillary thyroid cancers are caused by changes to the BRAF gene in your body, but this isn't something you can control.
Just a few things raise your odds of getting thyroid cancer:
Inherited genetic syndromes. Some conditions, including cancer, come from the DNA you get from your parents. In 2 out of 10 cases of medullary thyroid cancer (MTC), for example, the cancer is a result of an abnormal gene you’ve inherited.
Iodine deficiency. If you don’t get much of this chemical element in your diet, you could be at more risk for certain types of thyroid cancer. This is rare in the U.S. because iodine is added to salt and other foods.
Radiation exposure. If your head or neck was exposed to radiation treatment as a child, you could have a higher cancer risk.
There isn't a screening test for thyroid cancer. Your doctor may find out you have it during a routine physical exam or from an ultrasound or surgery for another condition.
Who Gets It?
Risk factors for thyroid cancer include:
- Sex. Thyroid cancer is 3 times more common in women than men, though the reason is unclear. Women tend to get thyroid cancer in their 40s and 50s, while men who get it are usually in their 60s or 70s.
- Race. Follicular thyroid cancer is more common in White people than Black people.
- Age. Thyroid cancer is most common in people in their 30s to their 60s, for unknown reasons.
- Family history. If a near relative had thyroid cancer, your chances of getting it are higher, but most people who get it have no family history.
- Certain inherited genes. These make up only a small percentage of the people who get the condition.
- Excess body weight. Being overweight or obese increases your risk of getting thyroid cancer.
Thyroid Cancer Treatment
Thyroid cancer is usually very treatable, even if you have a more advanced stage of it. The sort of treatment you get depends on the type of thyroid cancer you have and the stage it is at. Here are some common methods of treatment:
Surgery
This is part of treatment for nearly all types of thyroid cancer. You might have a thyroidectomy (a removal of your thyroid), which means you'll have to take thyroid hormone pills for the rest of your life. Or you might get a lobectomy (removal of one of your thyroid lobes if just one is cancerous). If so, you may not need to take thyroid hormones.
Your lymph nodes might also need to be removed surgically if the cancer has spread there.
Radiation therapy
This is often given after surgery to make sure the cancer doesn't return or to kill cells your surgeon may not have removed. You may get radiation therapy in a few ways:
- External radiation therapy. A machine outside your body sends radiation to the area of your body that had the cancer.
- Internal radiation therapy. A radioactive substance enclosed in a needle, wire, or catheter is placed into or near the cancer.
- Radioactive iodine (RAI) therapy. Radioactive iodine is given as a pill, liquid, or shot. This destroys cells that take up iodine, which are mainly found in your thyroid gland.
Chemotherapy
Drugs to kill cancer cells are given either by mouth or as a shot. This isn't often needed when you have thyroid cancer.
Hormone Therapy
Taking high doses of the thyroid hormone can slow the growth of thyroid cancer cells and the risk of thyroid cancer returning. This is because when the level of thyroid hormone is high, your pituitary gland makes lessthyroid stimulating hormone (TSH). TSH promotes the growth of the thyroid gland and probably of thyroid cancer cells.
Targeted Therapy
This uses drugs to kill certain cancer cells. While chemotherapy kills all fast-growing cells, including cancer cells, targeted therapies go after specific genes and proteins inside cancer cells. These targeted drugs are called kinase inhibitors. Kinases are proteins that signal to cancer cells to grow. A kinase inhibitor would block these signals.
Targeted therapies are used when other treatments have not stopped your thyroid cancer.
Complications of Thyroid Cancer
If your thyroid cancer isn't treated, it could spread to your airways, esophagus (food pipe), and other structures. It could also spread to more distant body body parts, like your lungs, bones, and other soft tissues, and possibly be fatal.
If you have a lobectomy or total thyroidectomy, you may get temporary or permanent hoarseness or loss of voice because of nerve damage or irritation from the breathing tube used in surgery. In severe cases, you might have breathing problems too.
You might get low calcium levels from an accidental removal of the parathyroid glands during surgery. These glands are behind the thyroid, and they help to regulate calcium levels. Removal of these glands may also cause muscle spasms and tingling.
Complications from thyroid surgery are unusual if you have an experienced surgeon doing the procedure.
Thyroid Cancer Prognosis
The outlook is generally very good. The five-year relative survival rate for thyroid cancer is 95% for all races and ages. This means that, on average, you're 95% as likely to be alive in five years as someone who didn't have thyroid cancer.
Of course, the survival rate changes depending on the stage and type of your cancer.
For papillary and follicular thyroid cancer, the five-year survival rates are 99.5% and 98%, respectively.
For medullary thyroid cancer, the five-year rate is 91%. For anaplastic cancer, the five-year rate is 8%.
Statistics are from the National Cancer Institute. They only apply to the stage of cancer when it was first diagnosed. They don't apply if the cancer comes back after treatment or spreads.
Thyroid Cancer Prevention
Most of the time, thyroid cancer can't be prevented. Most people get it for no known reason. But there are a few things you can do to reduce your risk.
Limit radiation exposure. Radiation exposure is a known risk factor for thyroid cancer, especially for children. If you or your child must have an imaging test (like an X-ray or CT scan), make sure your doctor or dentist uses shields to protect the head, neck, and body from radiation.
Keep a healthy body weight. Being overweight raises your risk of thyroid cancer.
Check if you're at high risk of thyroid cancer. This normally means you have family members who have had thyroid cancer. Talk to your doctor about having genetic testing to see if you carry the gene multiple endocrine neoplasia type 2 (MEN2), which puts you at high risk of MTC. Your doctor can also advise you on next steps if it turns out you do have the gene. Some people with this gene have opted for removal of their thyroids as a preventive measure.
Ozempic and Thyroid Cancer
Ozempic is a brand name of the drug semaglutide. Originally used to treat type 2 diabetes, it has become very popular for weight loss. Other brand names for semaglutide are Wegovy and Rybelsus. These drugs work for weight loss by tricking the brain so that you feel full faster and for a longer period of time.
The FDA has issued a boxed warning for Ozempic, Rybelsus, and Wegovy stating that studies in rodents have shown semaglutide caused thyroid C-cell tumors, and therefore people with a personal or family history of MTC should avoid taking it.
But studies published in 2024 showed there was little to no increased risk of contracting thyroid cancer while on these drugs. One study reported that the incidence of thyroid cancer in semaglutide-treated patients was less than 1%.
As of now, the FDA warning stands. So if you do have a family or personal history of MTC, be sure to tell your doctor before taking one of these drugs, whether for diabetes or weight loss.
Takeaways
Thyroid cancer starts when abnormal cancer cells change, or mutate, in your thyroid, a gland in your throat that controls your metabolism. The abnormal cells begin multiplying and, once there are enough of them, they form a tumor in your thyroid. You may see a swelling in your neck or throat. This type of cancer is very treatable. Treatment usually involves surgery to remove all or part of your thyroid followed by radiation therapy. The five-year survival rate is around 95%.
Thyroid Cancer FAQs
Is thyroid cancer serious?
It is serious but very curable.
Is thyroid cancer 100% curable?
It depends on the stage and type you have, but the most common types have cure rates of 98%-99.5%.
What is the first stage of thyroid cancer?
Stage I cancer (if you're under 55) means your tumor is any size and hasn't spread to nearby lymph nodes or other body parts. If you're over 55, it means that your tumor is completely inside your thyroid but no more than 4 centimeters (1.6 inches) across and it hasn't spread to nearby lymph nodes or other body parts.
Can thyroid cancer come back after a total thyroidectomy?
It come back even 20 years after treatment, as it's slow-growing. So it's important to keep following up with your doctor.
Can smoking cause thyroid cancer?
One review of 24 studies found that current smokers have a lower risk of getting thyroid cancer, implying that smoking has some sort of protective effect. But it's well-known that smoking can cause other kinds of cancer, particularly lung cancer. So don't take this as advice to start smoking.
