Medullary Thyroid Cancer (MTC)

What is medullary thyroid cancer (MTC)?

Medullary thyroid cancer (MTC) is cancer that forms inside your thyroid gland, which is called the medulla. The medulla contains special cells called parafollicular C cells that produce and release a hormone called calcitonin. MTC happens when the C cells become cancerous and grow out of control.

Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. It’s a part of your endocrine system and controls many of your body’s important functions by producing and releasing (secreting) certain hormones.

The majority of MTC cases are sporadic, meaning there’s no specific cause. About 25% of cases are due to an inherited condition called multiple endocrine neoplasia type 2.

MTC is also called medullary thyroid carcinoma.

What's the difference between papillary and medullary thyroid cancer?

Papillary thyroid cancer is the most common type of thyroid cancer, representing about 80% of all thyroid cancer diagnoses, whereas medullary thyroid cancer (MTC) is more rare and accounts for around 2 %.

Papillary thyroid cancer begins in the thyroglobulin-producing follicular cells in your thyroid, whereas MTC arises from calcitonin-producing cells in your thyroid. Thyroglobulin is a protein, and calcitonin is a hormone.

Papillary thyroid cancer is often linked to radiation exposure, whereas MTC is not.

What is the difference between medullary and follicular thyroid cancer?

Follicular thyroid cancer is the second most common type of thyroid cancer. This cancer begins in the follicle cells of your thyroid, which are the functional and structural units of the gland. They release thyroid hormone.

Medullary thyroid cancer begins in the calcitonin-producing cells of your thyroid (called C cells).

Who does medullary thyroid cancer affect?

Anyone can get medullary thyroid cancer (MTC), but you’re very likely to get MTC if you have multiple endocrine neoplasia type 2 (MEN2), an inherited condition.

Sporadic medullary thyroid cancer most commonly occurs during the fifth or sixth decade of life. Medullary thyroid cancers associated with MEN2 most commonly occur around the second or third decade of life.

People assigned female at birth are more likely to develop sporadic MTC than people assigned male at birth.

How common is medullary thyroid cancer (MTC)?

Thyroid cancer is fairly common, but medullary thyroid cancer (MTC) is rare. Approximately 2% to 4% of all thyroid cancers in the United States are MTC. About 1,000 people are diagnosed with MTC each year in the U.S.

Where does medullary thyroid cancer (MTC) spread to?

Medullary thyroid cancer can, and frequently does, spread (metastasize) to your lymph nodes (in your lymphatic system) and other organs, including your:

• Lungs.
• Liver.
• Bones.
• Brain.

What are the signs and symptoms of medullary thyroid cancer (MTC)?

Signs and symptoms of medullary thyroid cancer (MTC) include:

• A nodule (lump) on the upper part of your thyroid gland (75% to 95% of people have this at diagnosis).
• Swollen lymph nodes (lymphadenopathy) in your neck (70% of people have this at diagnosis).
• An enlarged thyroid nodule, which can cause hoarseness, difficulty swallowing or breathing issues (this is less common).

In some cases, people have MTC for a long time before they notice symptoms because the tumor remains small.

What causes medullary thyroid cancer?

About 75% of medullary thyroid cancer (MTC) cases are sporadic, meaning it happens in people who don’t have a family history of MTC or an inherited change in their DNA that would increase their risk for MTC. Scientists haven’t yet figured out the exact cause of sporadic MTC.

In up to 25% of cases, MTC is due to an inherited condition called multiple endocrine neoplasia type 2 (MEN2).

MEN2 is a rare genetic cancer syndrome characterized by a very high likelihood of MTC and an increased risk of developing other tumors (neoplasia) affecting additional glands in your endocrine system.

People with MEN2 have at least one copy of a mutation (change) of the RET or CDKN1B gene. Affected people often inherit the altered gene from one biological parent. Some cases, however, result from new mutations in the gene and occur in people without other affected family members.

There are different subtypes of MEN2, including:

• MEN2A: People with MEN2A have a high chance (90%) of getting MTC. They’re also at risk (30% to 50%) for getting pheochromocytoma (a tumor in your adrenal glands) and/or primary hyperparathyroidism. MEN2A may also be called Sipple syndrome or PTC syndrome.
• MEN2B: MEN2B can sometimes be inherited, but most of the time, it isn’t. People with MEN2B have a 100% chance of getting MTC at a very young age. They also have a 50% chance of getting pheochromocytoma at some point in their life. MEN2B is also called Wagenmann–Froboese syndrome or MEN3.

There’s also a sub-variant of MEN2B called familial medullary thyroid cancer (FMTC). People with FMTC have a RET gene mutation but only develop MTC.

Approximately 95% of people with multiple endocrine neoplasia type 2 have the MEN2A subtype.

How is medullary thyroid cancer (MTC) diagnosed?

Medullary thyroid cancer usually presents as a lump or nodule on your thyroid gland. You may notice it or your healthcare provider may discover it during a routine neck examination. Sometimes, the nodule is discovered incidentally (accidentally) by imaging tests you get for other medical reasons.

Your provider will likely order the following tests to help diagnose MTC:

• Imaging tests: Your provider may order imaging tests to identify the nodule on your thyroid. These tests might include thyroid ultrasound, CT (computed tomography) scan and/or magnetic resonance imaging (MRI).
• Fine needle aspiration (needle biopsy): Your provider will likely want to take a small tissue sample, called a biopsy, from the nodule on your thyroid using a very thin needle. A pathologist will look at the tissue under a microscope to see if there are cancer cells and, if so, what type of thyroid cancer it is.
• Blood tests: Your provider may order blood tests, including ones that measure the amount of calcitonin and carcinoembryonic antigen (CEA) in your blood. These levels are typically elevated in people with MTC.

Your provider may also recommend genetic counseling to see if you have multiple endocrine neoplasia type 2 (MEN2), which is the cause of about 25% of MTC cases. If you do have MEN2, they’ll recommend genetic counseling for your biological family members as well.

How is medullary thyroid cancer treated?

The main treatment for MTC is surgery to remove your entire thyroid gland (total thyroidectomy).

If you have thyroid cancer present in the lymph nodes in your neck, your surgeon will likely remove the affected lymph nodes during your thyroid surgery. After surgery, you’ll need to take thyroid hormone replacement medications for the rest of your life.

Other than surgery, your healthcare provider may recommend other treatments, including:

• Radiation therapy.
• Chemotherapy.
• Targeted therapies that act on changes in DNA found in some cases of MTC.

After treatment for MTC, your provider will monitor your levels of a tumor marker called CEA and calcitonin levels through blood tests. This way they can keep track of how well the treatment is working or if cancer has come back.

MTC is usually more aggressive than the other more common types of thyroid cancer. It’s usually easier to treat and manage if it’s found before it spreads to lymph nodes in your neck or other parts of your body.

Can medullary thyroid cancer (MTC) be prevented?

Many people develop medullary thyroid cancer (MTC) for no known reason (known as sporadic cases), so prevention isn’t possible.

But if you have a family history of MTC and/or multiple endocrine neoplasia type 2 (MEN2) and have tested positive for the RET gene mutation, then you may be able to get preventive (prophylactic) surgery to remove your thyroid gland before cancer develops.

At the very least, it’s important to let your healthcare provider know if you have a family history of MTC and/or (MEN) so that they can carefully monitor the health of your thyroid.

What is the prognosis (outlook) for medullary thyroid cancer (MTC)?

The prognosis (outlook) for medullary thyroid cancer (MTC) depends on several factors, including:

• The stage of the cancer.
• If the cancer has spread to other parts of your body (metastasized).
• How much of the tumor was taken out during surgery.
• Your age and overall health.

The prognosis of MTC is usually not as favorable as papillary and follicular thyroid cancers. But, if MTC is discovered early, surgery can be curative. Even in cases where it’s not caught early, MTC often progresses relatively slowly.

Older people, those with late-stage cancer and those who have incomplete surgical removal of the tumor have a worse prognosis.

What is the life expectancy of medullary thyroid cancer?

Current research estimates that the five-year survival rate for stages 1 to 3 of medullary thyroid cancer is 93% and 28% for stage 4.

However, since there are so few new MTC cases diagnosed each year, these survival rates may not be very accurate.

When should I see my healthcare provider about medullary thyroid cancer?

If you’ve been diagnosed with medullary thyroid cancer, you’ll need to see your healthcare team regularly to monitor your treatment progress and to monitor your blood levels of calcitonin and CEA.

If you had your thyroid removed as part of treatment, you’ll need to take thyroid hormone medication for the rest of your life. Your provider will want to monitor your thyroid hormone levels throughout your life to make sure your medication dosage is working for you.

If you have multiple endocrine neoplasia type 2, it’s especially important to see your provider regularly to monitor your health and to catch other endocrine tumors, if they develop, in their earliest phases.

A note from Cleveland Clinic

Receiving a cancer diagnosis is unsettling, regardless of the type. Fortunately, medullary thyroid cancer (MTC) generally responds well to treatment if it’s caught early. While most MTC cases have an unknown cause, there’s a significant link to certain inherited conditions. If you or one of your first-degree relatives have been diagnosed with MTC, it’s important to go through genetic testing to make sure you don’t have a genetic condition that could potentially cause other medical issues. If you have any questions about your risk of developing MTC, talk to your healthcare provider. They’re available to help you.