What Is Medullary Thyroid Cancer?

Have you noticed a lump on the base of your neck that will not go away? This could be due to a thyroid nodule. Even though most thyroid nodules are not dangerous, have no symptoms, and only a small proportion of thyroid nodules are malignant, early diagnosis and appropriate management are essential for recovery. Thyroid cancers are classified into four categories, with medullary thyroid cancer (MTC) accounting for 3% to 4% of all thyroid malignancies. 

Overview

The thyroid gland is located in the base of the front of the neck, directly below the Adam's apple. It is in charge of delivering thyroid hormones to the rest of your body. Thyroid cancer develops when normal thyroid cells transform into malignant (cancerous) cells and spread uncontrollably. There are various forms of thyroid cancer, the most common ones include: papillary thyroid carcinoma, follicular thyroid cancer, anaplastic thyroid carcinoma, and medullary carcinoma.¹ 

Medullary thyroid cancer (MTC) is a type of cancer that originates in the medulla, the inner part of the thyroid gland. The medulla contains parafollicular C cells, which generate and release the hormone - calcitonin. MTC occurs when C cells become malignant and grow out of control. MTC can, and typically does, spread to the lymph nodes, as well as other organs. 

Causes of medullary thyroid cancer

Numerous factors influence a person's risk of getting cancer, including age, genetics, and exposure to certain risk factors (including some possibly avoidable lifestyle factors). Thyroid cancer affects 1 in 332 people assigned male at birth (AMAB)  and 1 in 170 people assigned female at birth (AFAB) in the United Kingdom.

The majority of medullary thyroid carcinomas are sporadic, which refers to a disease that develops on an irregular and occasional basis.² However, as part of  multiple endocrine neoplasia type 2 (MEN2) syndrome, around 25% run in the family.² MEN2 and familial medullary thyroid carcinoma (FMTC) are linked to gene modifications in the reproductive cells (egg or sperm) that become incorporated into the DNA of the offspring's cells (germline mutations) .^2,3 

Multiple endocrine neoplasia type 2 (MEN2) is divided into two different syndromes (MEN2A and MEN2B), each of which is autosomal dominantly transmitted and associated with MTC. 

Signs and symptoms of medullary thyroid cancer

People may not detect any symptoms initially, but they may discover they have thyroid cancer when their doctor does a neck imaging or physical exam for another reason.

The most common sporadic MTC presentation is a solitary thyroid nodule, which occurs in 75-95% of individuals.⁶ Because C cells mainly reside in the upper portion of thyroid glands, most tumours are found in this area. When most people with MTC are diagnosed, the disease has already spread (metastasised). Around 70% of individuals have clinically apparent cervical lymph node involvement, 15% have dysphagia, difficulty swallowing, hoarseness, or are unable to talk, and 5-10% have distant metastatic disease.^4,7 Distant metastases can develop in the liver, lungs, bones, and, less frequently, the brain and skin.⁸

Systemic symptoms can develop as a result of the tumour's hormonal release. In patients with severe disease, tumour release of calcitonin or other chemicals might produce diarrhoea or facial flushing.

Management and treatment for medullary thyroid cancer

Medullary thyroid cancer is often diagnosed following a fine-needle aspiration (FNA) biopsy in a patient with a solitary thyroid nodule, during which a thin needle is used for collecting a small sample of cells from the lesion. 

Because of the frequent cases of falsely high blood calcitonin measurements, the utility of serum calcitonin screening to supplement ultrasonography and FNA in the routine detection of thyroid nodules is controversial. 

According to the National Comprehensive Cancer Network (NCCN) and American Thyroid Association (ATA) Guidelines for Management of Medullary Thyroid Cancer, for patients diagnosed with MTC based on a cytologic assessment of a thyroid nodule, further evaluation should include blood tests such as serum calcitonin and carcinoembryonic antigen (CEA), ultrasonography of the neck (if not already performed), genetic testing for germline RET mutations, and biochemical testing.⁴

MTC management involves a multifaceted strategy that includes surgery, medical therapies, genetic testing, long-term monitoring, and supportive care. 

The primary treatment for MTC is surgery, which aims to remove malignant thyroid tissue as well as afflicted lymph nodes. Genetic testing aids in the identification of hereditary forms of MTC and guides treatment decisions. In severe situations, medical therapy such as tyrosine kinase inhibitors (TKIs) and calcitonin-lowering medications are utilised to halt cancer growth and improve symptoms. 

To detect recurrence or metastasis, long-term surveillance is required, which includes physical examinations, blood tests, imaging scans, and biopsies as needed. Supportive care focuses on symptom management as well as emotional support.

FAQs

How is medullary thyroid cancer diagnosed?

MTC is diagnosed using a combination of clinical evaluation, imaging studies, blood testing, and biopsy procedures.⁴ A complete medical history is taken, a physical examination is performed to check the thyroid gland and lymph nodes in the neck, and imaging techniques such as ultrasound, CT scan, and MRI are used to see the tumour and identify its extent. Blood tests, such as calcitonin and carcinoembryonic antigen (CEA) levels, can help with the diagnosis and monitoring of MTC.^4,9 A biopsy is often used for confirmation of a final diagnosis, which may require fine-needle aspiration or surgical removal of a tissue sample for inspection under a microscope.⁹

How can I prevent medullary thyroid cancer?

While it is not possible to totally avoid medullary thyroid carcinoma (MTC), various precautions can help minimise the risk or detect cancer at an early stage. 

Genetic testing is important, particularly for people with a family history of MTC or known genetic syndromes associated with the disease, such as MEN2.¹⁰ Regular medical check-ups and neck examinations can help identify thyroid conditions or nodules early. Thyroid ultrasound screenings can also be considered for people at a higher risk. 

Individuals with confirmed genetic mutations may choose preventive thyroidectomy, which includes surgically removing the thyroid gland to reduce the risk of developing MTC.¹⁰ Consultation with healthcare professionals, particularly genetic counsellors or endocrinologists, is required to evaluate personal risk factors and select the best preventative measures and screening procedures.

Who is at risk of medullary thyroid cancer?

Medullary thyroid cancer (MTC) may develop in people with a hereditary predisposition as well as those who have no family history of the disease. The following groups of persons are more likely to acquire MTC:

• Genetic predisposition: The hereditary type of MTC is linked to particular genetic alterations, most notably the RET proto-oncogene. Individuals with RET gene mutations, such as those with multiple endocrine neoplasia type 2A (MEN2A), MEN2B, or familial medullary thyroid cancer (FMTC), are at a higher risk of developing MTC^2,10
• Individuals with a family history of MTC or other genetic disorders associated with MTC are at a higher risk. Close relatives of those with hereditary MTC or known RET gene mutations may be at risk as well⁴
• Sporadic MTC: This type of MTC occurs when there is no known genetic mutation or family history. While the specific causes are unknown, several characteristics, such as older age and female gender, have been associated with an increased risk of sporadic MTC

Individuals with a familial predisposition to MTC have a much higher risk of developing the disease than those with sporadic cases. Genetic testing and counselling are essential for identifying at-risk individuals and implementing appropriate screening and preventive actions. Healthcare specialists, particularly genetic counsellors and endocrinologists, can offer advice and personalised risk assessments based on an individual's specific situation.

How common is medullary thyroid cancer?

When compared to other forms of thyroid cancer, medullary thyroid carcinoma (MTC) is rather uncommon. It is responsible for about 3-4% of all thyroid cancer cases. The frequency of MTC, however, varies depending on the population studied and the existence of certain genetic abnormalities linked to the disease.

Hereditary MTC account for a lesser proportion of cases but has a higher likelihood of multiple tumours and a more aggressive course. Hereditary types of MTC account for 25-30% of all MTC cases.² The majority of cases, on the other hand, are sporadic MTC, which arises without a family history or known genetic mutation.² While the exact prevalence of sporadic MTC is unknown, it is thought to be less prevalent than papillary and follicular thyroid cancers.

When should I see a doctor?

If you have any concerning symptoms or if you have risk factors for medullary thyroid carcinoma (MTC), you should consult a doctor. Here are some examples of when you should see a doctor:

• Symptoms: Seek medical assistance if you experience any persistent or odd symptoms related to the thyroid or neck area. A lump or swelling in the neck, trouble swallowing, hoarseness or changes in voice, persistent cough, unexplained weight loss, or changes in bowel habits are all common symptoms of MTC
• Family History: If you have a family history of MTC or other genetic syndromes associated with MTC, you should see a doctor. They can analyse your risk and advise you on the best genetic testing or screening options for you
• Known Genetic Mutation: If you have already been diagnosed with a genetic mutation linked to MTC, it is critical to continue with frequent check-ups and tests as directed by your healthcare professional

Remember, if you have any symptoms or particular risk factors for MTC, it is always better to speak with a healthcare professional. They can assess your condition, order required tests, and advise you on the next measures to take.

Summary

Medullary thyroid cancer (MTC) is a relatively rare form of thyroid cancer that originates from the parafollicular C cells in the thyroid gland. MTC can occur in both hereditary and sporadic forms and is known for its potential aggressiveness and tendency to metastasize early. 

Common symptoms include a palpable lump in the neck, difficulty swallowing, voice changes, coughing, unexplained weight loss, and changes in bowel habits. Diagnosis involves a combination of clinical evaluation, imaging tests (such as ultrasound, CT scan, and MRI), blood tests (including measurement of calcitonin levels), and biopsy. 

Management of MTC typically involves a surgical intervention to remove the thyroid gland and affected lymph nodes, as well as genetic testing to identify hereditary forms and guide treatment decisions. Medical therapies, such as tyrosine kinase inhibitors (TKIs) and calcitonin-lowering drugs, may be used in advanced or metastatic cases. Long-term monitoring and supportive care are also integral parts of MTC management. Individuals with a family history of MTC or known genetic mutations should consider regular screenings and genetic counselling.