Medullary thyroid cancer, or MTC, is a cancer that forms in the thyroid. The thyroid is a gland located in the front of your neck, just below the Adam’s apple. It is responsible for sending out hormones to the rest of your body. The inside of the thyroid is called the medulla. The medulla contains special cells called parafollicular C cells that produce and release hormones. MTC happens when the C cells become cancerous and grow out of control. MTC may also be called medullary thyroid carcinoma.

Thyroid cancer is fairly common. There are four different types of thyroid cancers and MTC is the rarest type making up 3% to 4% of all thyroid cancers. About 1,000 people are diagnosed with MTC each year in the U.S.

MTC can start as a lump in the throat. The tumor growing in the thyroid can make your voice hoarse by blocking your vocal chords or it can make it hard to breathe by blocking your windpipe. Sometimes people can have MTC for a long time without symptoms because the tumor remains small. MTC can spread to other organs, such as lung, liver, bones, and brain.

Imaging: MTC is diagnosed by your doctor first feeling your throat to check for a lump, followed by imaging scans of the thyroid. Imaging scans might include ultrasound, CT, or MRI.

Biopsy: The doctor will also want to take out a small amount of tissue, called a biopsy, from the thyroid using a very thin needle. A pathologist will look at the tissue under the microscope to see if there are cancer cells and, if so, what type of thyroid cancer it is.

MTC is usually treated by removing the thyroid. This surgery is called a thyroidectomy. In certain people with a high risk for MTC, such as people carrying certain gene changes, a thyroidectomy may be performed to prevent cancer.

Besides surgery, sometimes other treatments are also required, including radiation therapy or chemotherapy. Also, targeted therapies are available that act on changes in DNA found in some cases of MTC.

After treatment, your doctor will monitor levels of a tumor marker called CEA and the hormones produced by C cells to keep track of how well the treatment is working or if cancer has come back. CEA is a type of tumor marker found in the blood of those with MTC.

Twenty-five percent of MTC cases run in families. MTC may be passed down when families carry a change in the RET gene that causes a condition called multiple endocrine neoplasia type 2, or MEN2. There are two types of MEN2: MEN2A and MEN2B.

MEN2A: If you have MEN2A, you have a high chance (90%) of getting MTC. You are also at risk (30% to 50%) for getting pheochromocytoma, a cancer of the adrenal glands. MEN2A is rare, affecting 1 in 40,000 people. MEN2A may also be called Sipple syndrome or PTC syndrome.

MEN2B: MEN2B can sometimes be passed from parent to child but most of the time, it isn’t. If you have MEN2B, you have a 100% chance of getting MTC at a very young age. You also have a 50% chance of getting pheochromocytoma at some point in your life. MEN2B is also called Wagenmann–Froboese syndrome or MEN3.

Scientists are always working to understand how cancer forms but it can be hard to prove. We know that some MTC cases have changes in the RET gene. MTC is also more common in females than males. This information gives scientists clues about how MTC forms and can lead to new treatments.

The estimate of how a disease will affect you long term is called prognosis. Every person is different and prognosis will depend on many factors, such as:

• If the cancer has spread to other parts of your body
• If the cancer responds to chemotherapy
• How much of the tumor was taken out during surgery

If you want information on your prognosis, it is important to talk to your doctor. NCI also has resources to help you understand cancer prognosis.

Doctors estimate MTC survival rates by how groups of people with MTC patients have done in the past. Given that there are so few MTC patients, survival rates may not be very accurate. They also don’t consider newer treatments being developed. We know that people can live with MTC for many years, even though there is no cure.