Medullary Thyroid Cancer

What is medullary thyroid cancer?

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

Hearing you might have cancer can leave you with many questions and worries, especially when it’s rare. Know that your healthcare team will be by your side along the way. Several therapies can help treat MTC.

How common is medullary thyroid cancer?

Thyroid cancer, in general, is fairly common. But medullary thyroid cancer, specifically, is rare. Approximately 4% to 10% of all thyroid cancers in the United States are MTC. About 1,000 people receive an MTC diagnosis each year in the U.S.

What are the symptoms of medullary thyroid cancer?

Symptoms of medullary thyroid cancer include:

• A nodule (lump) on the upper part of your thyroid gland (75% to 95% of people have this at diagnosis)
• Swollen lymph nodes in your neck (70% of people have this at diagnosis)

In rare cases, an enlarged thyroid nodule can cause:

• Hoarseness
• Difficulty swallowing
• Breathing issues

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

What causes medullary thyroid cancer?

About 75% of medullary thyroid cancer (MTC) cases (3 in 4) are sporadic. This means it happens in people who don’t have a family history of MTC. Scientists haven’t yet figured out the exact cause of sporadic MTC. But 40% to 50% of people with sporadic MTC have acquired mutations in the RET gene. This means you develop the genetic mutation later in life — you aren’t born with it.

In up to 25% of cases (1 in 4), MTC is due to an inherited condition called multiple endocrine neoplasia type 2 (MEN2). There are different subtypes of MEN2, including:

• MEN2A. People with MEN2A have a high chance (90%) of getting MTC.
• MEN2B. Some cases of MEN2B are inherited. But most of the time, it isn’t. People with MEN2B have an 100% chance of getting MTC at a very young age.

There’s also a subvariant of MEN2B called familial medullary thyroid cancer (FMTC). People with FMTC have a RET gene mutation but only develop MTC (not other tumors).

If you have the RET gene mutation, you may be able to get preventive surgery to remove your thyroid gland before cancer develops.

How is medullary thyroid cancer 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 exam. Sometimes, providers discover it accidentally with imaging tests you get for other reasons.

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

• Imaging tests. Imaging tests can help identify the nodule on your thyroid. These tests might include thyroid ultrasound, a CT scan and/or MRI.
• Fine needle aspiration (needle biopsy). Your provider will likely want to take a small tissue sample (biopsy) from the nodule on your thyroid. They’ll use a very thin needle.
• Blood tests. These may include tests that measure your levels of calcitonin and carcinoembryonic antigen (CEA). These levels are typically elevated in people with MTC.

Your provider may also recommend genetic testing to see if you have MEN2. If you do, they’ll recommend genetic testing for your biological family members, as well.

What is the treatment for medullary thyroid cancer?

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

If the thyroid cancer has spread (metastasized) to lymph nodes in your neck, your surgeon will likely remove them, as well. 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 (vandetanib and cabozantinib)

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

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

What is the prognosis for someone with 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 good as papillary and follicular thyroid cancers. But if you and your provider discover MTC early, surgery can cure it. Even if the diagnosis is delayed, MTC often progresses (gets worse) relatively slowly.

A worse prognosis may affect those:

• Who are over 65 years
• Have late-stage cancer
• Have incomplete surgical removal of the tumor

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%. It’s 28% for stage 4.

It’s important to note that since there are so few new MTC cases diagnosed each year, these survival rates may not be very accurate. Your healthcare team will give you a better idea of what to expect.

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

Papillary thyroid cancer is the most common type of thyroid cancer. It represents about 80% of all thyroid cancer diagnoses. Medullary thyroid cancer (MTC) is rare.

Papillary thyroid cancer begins in the thyroglobulin-producing follicular cells in your thyroid. 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 isn’t.