Thyroid cancer, medullary

Other Names: Thyroid carcinoma, medullary; Medullary thyroid cancer (MTC)

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.

Cause

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.

Inheritance

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.

Signs and symptoms

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. The major clinical symptom of metastatic medullary thyroid carcinoma is diarrhea; occasionally a patient will have flushing episodes. Both occur particularly with liver metastasis, and either symptom may be the first manifestation of the disease. The flushing that occurs in medullary thyroid carcinoma is indistinguishable from that associated with carcinoid syndrome. In MTC, the flushing, diarrhea, and itching (pruritus) are all caused by elevated levels of calcitonin gene products (calcitonin or calcitonin gene-related peptide).By comparison, the flushing and diarrhea observed in carcinoid syndrome is caused by elevated levels of circulating serotonin. Medullary thyroid carcinoma may also produce a thyroid nodule and enlarged cervical lymph nodes. Sites of spread of medullary thyroid carcinoma include local lymph nodes in the neck, lymph nodes in the central portion of the chest (mediastinum), liver, lung, and bone. Spread to other sites such as skin or brain occurs but is uncommon.

Diagnosis

Medullary thyroid carcinoma on ultrasound with typical small calcifications (arrows)

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.

Treatment

A surgery for MTC showing the central lymph nodes and thyroid gland removed

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.

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Vandetanib Treatment of asymptomatic or progressive medullary thyroid cancer in patients with unresectable locally advanced or metastatic disease.
• Cabozantinib (Brand name: Cometriq)Treatment of progressive, metastatic medullary thyroid cancer (MTC).
• Thyrotropin alpha (Brand name: Thyrogen®) As an adjunctive diagnostic tool for serum thyroglobulin (Tg) testing with or without radioiodine imaging in the follow-up of patients with thyroid cancer.

Epidemiology

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.

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.

NIH genetic and rare disease info

• NIH info on Thyroid cancer, medullary

Thyroid cancer, medullary is a rare disease.

Thyroid cancer, medullary Resources
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