Medullary carcinoma of the thyroid is cancer of the thyroid gland that starts in cells that release a hormone called calcitonin. Such cells are called "C" cells.

Thyroid - medullary carcinoma; Cancer - thyroid (medullary carcinoma); MTC

The cause of medullary carcinoma of the thyroid (MTC) is unknown.

Unlike other types of thyroid cancer, MTC is less likely to be caused by radiation therapy to the neck given to treat other cancers during childhood.

There are two forms of MTC:

• Sporadic MTC, which does not run in families. Most MTCs are sporadic. This form mainly affects older adults.
• Inherited MTC runs in families.

You have an increased risk of this type of cancer if you have:

• A family history of MTC
• A family history of multiple endocrine neoplasia (MEN)
• A prior history of pheochromocytoma, mucosal neuromas, or hyperparathyroidism

Other types of thyroid cancer include:

• Anaplastic carcinoma of the thyroid
• Follicular tumor of the thyroid
• Papillary carcinoma of the thyroid
• Thyroid lymphoma

• Breathing problems due to narrowing of airways
• Cough
• Cough with blood
• Diarrhea
• Goiter (enlarged thyroid)
• Lump on thyroid gland

The health care provider will perform a physical exam. Lymph nodes in the neck may be swollen. Thyroid function tests are usually normal. However, an examination of the thyroid may reveal single or multiple nodules (lumps).

Other tests that may be used to diagnose MTC may include:

• Calcitonin blood test
• CEA blood test
• Genetic testing
• Thyroid biopsy
• Thyroid scan
• Ultrasound of the thyroid

Patients with MTC should be checked for certain other tumors, especially pheochromocytoma.

Treatment involves surgery to remove the thyroid gland and surrounding lymph nodes. Because this is an uncommon tumor, surgery should be performed by a surgeon who is familiar with this type of cancer.

Chemotherapy and radiation do not work very well for this type of cancer. Radiation is used in some patients after surgery. There are a number of new treatments currently being investigated in clinical trials.

For additional information, see cancer support groups.

Approximately 86% of those with medullary carcinoma of the thyroid live at least 5 years after diagnosis. The 10-year survival rate is 65%.

Complications may include:

• Cancer spreads to other areas of the body
• Parathyroid glands are accidentally removed during surgery

Call your health care provider if you have symptoms of medullary carcinoma of the thyroid.

Prevention may not be possible. However, being aware of your risk factors, especially your family history, may allow for early diagnosis and treatment. There are some recommendations regarding removing the thyroid gland in people who have a very strong family history of MTC. You should carefully discuss this option with a doctor who is very familiar with the disease.

Ladenson P, Kim M. Thyroid. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 244.

National Comprehensive Cancer Network. NCCN Guidelines in Oncology 2010: Thyroid Cancer. Version 1.2010.