Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) is a rare type of cancer that starts in specific cells of the thyroid gland called C cells. These cells produce a hormone called calcitonin. Unlike most other thyroid cancers, MTC often runs in families and can be part of genetic syndromes. Early detection and treatment, usually surgery, are crucial for a better outlook.

What is Medullary Thyroid Cancer?

Medullary thyroid cancer (MTC) is a rare form of cancer that develops from the C cells (also called parafollicular cells) of the thyroid gland. The thyroid gland is a butterfly-shaped organ located at the base of your neck, responsible for producing hormones that regulate metabolism. MTC accounts for a small percentage of all thyroid cancers.

The C cells in your thyroid gland produce a hormone called calcitonin, which helps control calcium levels in your blood. When these C cells become cancerous, they can produce abnormally high levels of calcitonin, which can be used as a marker for the disease. Unlike the more common types of thyroid cancer that arise from follicular cells, MTC behaves differently. It has a higher chance of spreading to nearby lymph nodes and other parts of the body, such as the liver, lungs, or bones, even at early stages. This makes early diagnosis and aggressive treatment particularly important. MTC is considered rare, making up about 1 to 2 out of every 100 thyroid cancers (1-2%). It can occur at any age, though it is often diagnosed in adults. Understanding its unique characteristics, including its genetic links, is key to effective management.

Symptoms

Medullary thyroid cancer (MTC) often does not cause noticeable symptoms in its early stages. When symptoms do appear, the most common sign is a lump or swelling in the neck, which may be felt or seen. Other symptoms can arise if the cancer grows larger or spreads to other parts of the body.

A lump in the neck is the most frequent symptom of MTC. This lump is usually painless and may be firm. You might notice it yourself, or a doctor might find it during a routine physical exam. If the lump grows, it can press on nearby structures, leading to other issues. Symptoms related to pressure on the windpipe (trachea) or food pipe (esophagus) can include difficulty swallowing (dysphagia) or a persistent cough. If the cancer affects the nerves controlling your vocal cords, you might experience hoarseness or other changes in your voice that do not go away. In some cases, MTC can cause symptoms related to the hormones it produces. High levels of calcitonin, produced by the cancerous C cells, can sometimes lead to chronic diarrhea. Flushing (redness and warmth of the skin) can also occur, though these symptoms are less common and usually appear in more advanced stages of the disease.

Causes & risk factors

Medullary thyroid cancer (MTC) is caused by genetic mutations, which are changes in your DNA. These mutations can be inherited from your parents, meaning they are passed down through families, or they can occur randomly during a person's lifetime without a family history of the disease.

About 75 out of 100 cases (75%) of MTC are sporadic, meaning they are not inherited. These cases result from a new genetic mutation that develops in the C cells during a person's life. The exact reason why these mutations occur is often unknown, and there are no clear lifestyle or environmental risk factors for sporadic MTC. The remaining 25 out of 100 cases (25%) of MTC are hereditary, meaning they are passed down through families. These inherited forms are caused by a specific mutation in a gene called RET (Rearranged during Transfection). If you have this mutation, you have a very high chance of developing MTC. Inherited MTC can occur as part of a genetic condition called Multiple Endocrine Neoplasia type 2 (MEN 2). There are two main types: MEN 2A and MEN 2B. Both types increase the risk of MTC, often at a younger age, and can also cause other tumors in different glands, such as the adrenal glands (pheochromocytoma) or parathyroid glands (hyperparathyroidism). Family members of someone with hereditary MTC are often advised to undergo genetic testing to check for the RET gene mutation.

How it's diagnosed

Diagnosing medullary thyroid cancer (MTC) typically involves a combination of physical examination, blood tests to check specific hormone levels, and imaging scans to visualize the thyroid and surrounding areas. A definitive diagnosis is usually made through a biopsy, where a small tissue sample is taken for examination under a microscope.

Your doctor will start with a physical exam, feeling your neck for any lumps or swollen lymph nodes. If a lump is found, blood tests are usually ordered. These tests measure levels of calcitonin and carcinoembryonic antigen (CEA), which are often elevated in people with MTC. High levels of these markers can suggest MTC, but they are not enough for a definitive diagnosis. Imaging tests help doctors see the thyroid gland and check for any suspicious areas. An ultrasound of the neck is often the first imaging test, as it can show the size and characteristics of thyroid nodules and check nearby lymph nodes. Other imaging tests, such as computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, or positron emission tomography (PET) scans, may be used to look for cancer spread (metastasis) if MTC is suspected or confirmed. The most important step for diagnosis is a biopsy, usually a fine-needle aspiration (FNA). During an FNA, a very thin needle is inserted into the thyroid lump, often guided by ultrasound, to collect a small sample of cells. These cells are then examined by a pathologist to determine if they are cancerous. If MTC is diagnosed, genetic testing for the RET gene mutation may also be recommended, especially if there is a family history of the disease.

Treatment options

The primary treatment for medullary thyroid cancer (MTC) is surgery to remove the thyroid gland. Depending on whether the cancer has spread, other treatments like targeted therapy, chemotherapy, or radiation therapy may be used. The best treatment plan is tailored to each individual, considering the stage of the cancer and overall health.

Surgery is the cornerstone of MTC treatment. This usually involves a total thyroidectomy, which is the complete removal of the thyroid gland. Because MTC often spreads to nearby lymph nodes, surgeons typically also remove lymph nodes in the neck (lymph node dissection) during the same operation. The extent of lymph node removal depends on whether cancer cells are found there. After surgery, blood tests for calcitonin and CEA are regularly performed to monitor for any remaining cancer cells or recurrence. If these markers remain high or rise, it may indicate that some cancer cells are still present or that the cancer has returned or spread. For MTC that has spread to other parts of the body (metastatic MTC) or cannot be completely removed by surgery, other treatments may be considered. Targeted therapy drugs, such as cabozantinib or vandetanib, are often used. These medications work by blocking specific pathways that cancer cells need to grow and survive. Chemotherapy and external beam radiation therapy are less commonly used for MTC but may be an option in certain situations, especially for controlling symptoms or treating specific areas where the cancer has spread.

Recovery & outlook

The recovery and outlook for medullary thyroid cancer (MTC) depend significantly on whether the cancer is confined to the thyroid gland or has spread at the time of diagnosis. Early detection and complete surgical removal offer the best chance for a positive outcome. Long-term follow-up care is essential to monitor for recurrence.

If MTC is found early and has not spread beyond the thyroid gland or to nearby lymph nodes, the outlook is generally good after successful surgery. However, MTC can be more aggressive than other types of thyroid cancer, and even with early treatment, there is a risk of recurrence or spread. After surgery, you will need lifelong follow-up care. This typically includes regular blood tests to measure calcitonin and CEA levels. A rise in these markers can be an early sign that the cancer has returned or spread. Imaging tests, such as ultrasound, CT, or MRI scans, may also be performed periodically to check for any signs of recurrence. For people with advanced MTC that has spread to distant parts of the body, the disease is more challenging to cure. However, treatments like targeted therapy can help control the cancer's growth and manage symptoms, improving quality of life and extending survival. Your medical team will work with you to create a personalized follow-up and treatment plan.

When to see a doctor

You should see a doctor if you notice any new or persistent lump or swelling in your neck. It is also important to seek medical attention for unexplained changes in your voice, difficulty swallowing, or chronic diarrhea that does not have an obvious cause. While these symptoms can be due to many conditions, they warrant evaluation.

If you discover a lump or swelling in your neck, even if it's painless, it's important to have it checked by a healthcare professional. Early detection of thyroid cancer, including MTC, can significantly improve treatment outcomes. Do not delay seeking medical advice for any new neck mass. Other symptoms that should prompt a visit to your doctor include persistent hoarseness or other voice changes that last for several weeks, difficulty swallowing food or liquids, or a chronic cough that doesn't go away. These could be signs that a growing mass in the neck is affecting nearby structures. Additionally, if you experience unexplained, ongoing diarrhea, especially if it's accompanied by flushing, you should discuss these symptoms with your doctor. While these are less common symptoms of MTC, they can be related to the disease, particularly in more advanced stages. Your doctor can help determine the cause of your symptoms and recommend appropriate diagnostic tests.

Frequently asked questions

Is Medullary Thyroid Cancer hereditary?

Yes, about 25 out of 100 cases (25%) of medullary thyroid cancer (MTC) are hereditary. These cases are caused by an inherited mutation in the RET gene and can be part of a genetic syndrome called Multiple Endocrine Neoplasia type 2 (MEN 2). Genetic testing is often recommended for individuals with MTC and their family members.

What is the RET gene?

The RET gene provides instructions for making a protein involved in cell growth and development. Mutations in the RET gene are linked to hereditary medullary thyroid cancer (MTC) and certain other endocrine tumors. Testing for this mutation can help identify individuals at risk and guide treatment decisions.

How is MTC different from other thyroid cancers?

Medullary thyroid cancer (MTC) is different because it originates from C cells (parafollicular cells) that produce calcitonin, unlike most other thyroid cancers that arise from follicular cells. MTC also has a higher tendency to spread to lymph nodes and other organs, and it often has a genetic, hereditary component.

Can Medullary Thyroid Cancer be cured?

Medullary thyroid cancer (MTC) can often be cured if it is detected early and completely removed through surgery before it has spread beyond the thyroid gland. For more advanced cases, while a cure may be less likely, treatments like targeted therapy can help control the disease and manage symptoms for many years.

What kind of follow-up care is needed after MTC treatment?

After treatment for medullary thyroid cancer (MTC), lifelong follow-up care is crucial. This typically involves regular blood tests to monitor calcitonin and CEA levels, which can indicate recurrence. Periodic imaging tests, such as ultrasound or CT scans, may also be performed to check for any signs of the cancer returning.

Are there specific dietary restrictions for MTC?

Generally, there are no specific dietary restrictions directly related to medullary thyroid cancer (MTC) itself. However, if you experience symptoms like chronic diarrhea due to high calcitonin levels, your doctor might suggest dietary adjustments to help manage these symptoms. Always discuss any dietary changes with your healthcare team.

Sources

• MedlinePlus — Medullary Thyroid Cancer
• Mayo Clinic — Medullary Thyroid Cancer
• Cochrane Library — Medullary Thyroid Cancer