Medullary thyroid cancer (MTC) is a rare type of thyroid cancer. It is often slow-growing.
MTC starts in cells in the thyroid gland called parafollicular cells or C cells. These cells normally make a hormone called calcitonin, which helps control the level of calcium in the blood.
About 5 to 9 out of 100 (5 to 9%) of thyroid cancers are MTC.
MTC may develop in people who have a rare inherited condition called multiple endocrine neoplasia (MEN).
The most common symptom of MTC is a lump in the neck, which may be painful.
Other symptoms may include:
- difficulty swallowing – a thyroid tumour pressing on the gullet (oesophagus) can cause this
- changes in breathing – a thyroid tumour pressing on the windpipe (trachea) can cause this
- a hoarse voice, for no obvious reason, that doesn’t go away after a few weeks
- a feeling of pressure or discomfort in the neck.
Less common symptoms include:
- a red face (flushing)
- frequent loose stools or diarrhoea.
These can be caused by the tumour making too much of the hormone calcitonin.
For most people, the cause of medullary cancer is unknown. This is called sporadic medullary thyroid cancer.
About 1 in 4 people (25%) who develop MTC have a rare inherited genetic condition called multiple endocrine neoplasia type 2 (MEN2). There are three types of MEN2:
- MEN2B (also called MEN3)
- familial medullary thyroid cancer (FMTC).
These are rare conditions. MEN2A and MEN2B can also cause growths (tumours) in other endocrine glands.
Almost everyone with MEN2 will develop MTC. Because of this, children and young adults with the MEN2 gene usually have an operation to remove the thyroid gland. This is to prevent cancer developing.
If you are diagnosed with MTC, you will be advised about a blood test to look for genetic changes. You are also likely to be referred to a specialist genetics service.
If you have symptoms, you will usually start by seeing your GP, who will examine you. If they are unsure what the problem is, or think your symptoms could be caused by cancer, they will refer you to a hospital for specialist advice and treatment. You should be seen at the hospital within two weeks.
If you have a family history of MEN2, your GP will also refer you to a specialist in genetic conditions for advice and treatment.
At the hospital, the doctor will ask you about your general health and any previous medical problems. The doctor will also take a detailed family history. They will examine you and you will have some of the following tests:
An ultrasound scan uses sound-waves to build up a picture of the inside of the neck and the thyroid gland. Your doctor will also check the lymph nodes in your neck to see if any of them are abnormal. This is because sometimes thyroid cancer can spread to the lymph nodes.
Fine needle aspiration (FNA)
A doctor gently passes a small needle into the lump or swelling in your neck. You may have a local anaesthetic to numb the area. Sometimes the doctor uses an ultrasound scanner to help guide the needle to the right area. Then they take a small sample of cells and examine it under a microscope to check whether there are any abnormal cells.
If an FNA does not collect enough cells, sometimes it is done again.
If the tests show you that have thyroid cancer, your doctor may want to do some further tests. These are to find out the size and position of the cancer and whether it has spread to other parts of the body. This is called staging and will help you and your doctor decide on the best treatment for you.
These tests may include the following:
These will check for the levels of calcitonin and calcium in your blood. You may also have a blood test to check the levels of a protein called CEA in the blood. CEA is a tumour marker. It can help your doctor monitor how well treatment is working.
24-hour urine sample
Some people who have MEN2 may have non-cancerous growths, called phaeochromocytomas on the adrenal glands. This test checks if the adrenal glands are affected. It is done even if there is no family history of MEN2.
CT scan (computerised tomography scan)
MRI scan (magnetic resonance imaging scan)
PET scan (positron emission tomography)
Vocal cord check
The treatment you have will depend on the stage of the cancer and your general health.
A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT).
The main treatments used are:
Other treatments include:
Some people may have radiolabelled therapies. This treatment uses a radioactive substance, which is attached to a particular type of chemical, to destroy the cancer. It is most likely to be used as part of a clinical trial.
Research trials are done to try to find new and better treatments for cancer. Because MTC is rare, it is difficult to research new treatments. Ask your thyroid specialist if there are any clinical trials suitable for you. clinicaltrials.gov is a website that has up-to-date international clinical trials, including UK trials.