Thyroid cancer

Thyroid cancer is the 5th most common cancer in women but accounts for only 0.3% of female mortality. There are nearly 140,000 new cases of thyroid cancer every year worldwide.

What is thyroid?

The thyroid is part of the endocrine system. It is a small butterfly-shaped gland located at the base of the neck, just below the Adam's apple. The thyroid weighs between 10 to 25 grams. It consists of two lobes, right and left, located on each side of the trachea. The lobes are connected by a thin piece of tissue called isthmus. In the thyroid, there are many small, rounded, sack-like structures called follicles. The follicles produce, store and release thyroid hormones.

What is the thyroid used for?

The thyroid is an endocrine gland, i. e. specialized in the production of hormones that will have an effect on the body. The hormones produced by the thyroid are called thyroid hormones. They help break down food into energy and also help regulate certain body functions such as body temperature, heart rate and breathing.

The thyroid produces 3 types of hormones:

  • tri-iodothyronine or T3;
  • tetra-iodothyronine or thyroxine, or T4. It is a reserve hormone that is produced in greater quantities than T3. At any time, if thyroid hormones are needed, T4 can be changed to T3 and become active.
  • calcitonin; it is also produced in smaller quantities by C cells (located between thyroid vesicles). It helps to regulate calcium metabolism throughout the body by reducing the level of calcium in the blood.

*The numbers 3 and 4 indicate the number of iodine atoms needed to make hormones. *

T4 is a hormone precursor, a kind of pre-hormone that, once in the blood, turns into T3.

T3 regulates metabolism, i. e. the level of activity of the body and organs, and therefore that of energy expenditure. The thyroid acts on the body temperature, the heart, the nervous system, the digestive tract, the genital system, the skin, the hair...

What is thyroid cancer?

Thyroid cancer is a malignant tumour that originates in the cells of the thyroid gland. A malignant tumour means that it can invade and destroy surrounding tissues. It can also spread (metastases) to other parts of the body.

Thyroid cells sometimes undergo changes that make their growth pattern or behaviour abnormal. These changes can lead to non-cancerous, or benign conditions such as hypothyroidism, hyperthyroidism, thyroid nodules, thyroiditis and goiter.

In some cases, modified thyroid cells can become cancerous. The most common types of thyroid cancer are papillary carcinoma and follicular carcinoma.

There are 4 main types of thyroid cancer:

Papillary cancer (80-85 % of cases)

The papillary type is a differentiated form of thyroid cancer, also known as well differentiated thyroid cancer. This means that cancer cells still look slightly like healthy cells. Well differentiated thyroid cancers are formed in the follicular cells of the thyroid gland.

If papillary thyroid cancer metastasizes (spreads), it is likely to be found in the neck nodes. People with papillary cancer often have more than one cancerous nodule in the thyroid gland and in the lymph nodes of the neck and/or chest.

Follicular cancer (7-15% of cases)

Like papillary thyroid cancer, follicular type is also a differentiated thyroid cancer. Although it is rare, if follicular thyroid cancer spreads, it is more likely to be found in the lungs or bones. Some patients have a mixed variant of follicular papillary type thyroid cancer.

Anaplastic cancer (1-2% of cases)

Anaplastic thyroid cancer is a very rare form of thyroid cancer. Anaplastic thyroid cancer nodules often remain undetected in the body for long periods of time. Since they are not treated, they suddenly become aggressive. Anaplastic thyroid cancer spreads rapidly and is much more difficult to treat.

Spinal cord cancer (3-5% of cases)

Like the differentiated forms of thyroid cancer that originate in the follicular cells of the thyroid gland, medullar type thyroid cancer originates in the C cells of the thyroid gland. C cells do not produce thyroid hormones and do not absorb iodine. For this reason, spinal cord cancer is not treated with radioactive iodine. Some blood tests are used to detect thyroid cancer of the medullary type.

What are the symptoms of the thyroid gland?

Thyroid cancer usually goes unnoticed in its early stages. It can then be discovered "by chance" during neck palpation or a cervical ultrasound performed for another cause. It can also be discovered when monitoring a goiter or a benign nodule. With its evolution, one or more of the following symptoms may appear, but they are in the vast majority of cases related to benign thyroid abnormalities or other more common pathologies:

  • More or less painful discomfort in the neck or throat;
  • Mass palpable or visible at the front of the neck or on the sides and corresponding to adenopathies (hypertrophy of the lymph nodes;
  • Change of voice, which becomes hoarse;
  • Difficulty swallowing or breathing;
  • More or less painful discomfort in the neck or throat;
  • Modification of a known nodule or goiter.

What tests should be done to detect thyroid cancer?

In 95% of cases, the nodules detected are of a benign nature: they are adenomas or cysts. The diagnostic check-up always begins with a complete client examination, with a palpation of the thyroid and a medical questionnaire on the personal and family history of thyroid disease.

If the doctor's doubts are proven, the following tests can be prescribed:

Thyroid check-up

The thyroid check-up is systematically requested by the doctor. It is a set of biological analyses carried out on the basis of a blood sample. It generally does not prejudge the malignant or benign nature of the nodule, but it does determine whether the thyroid function is normal or not. Most often only TSH is measured and the concentration of thyroid hormones (T3, T4) is only requested when there are clinical signs of hypo or hyperthyroidism. The level of calcitonin and calcium in the blood is sometimes required in the preoperative period.

Cervical and thyroid ultrasound

The examination of the neck area by ultrasound is systematically performed. This is a painless examination that allows the structure of the internal organs to be observed. During the ultrasound, the doctor measures the size of the thyroid gland, the number, size and shape of nodules and detects the possible presence of other abnormalities. He also looks to see if the neighbouring lymph nodes look normal. He is mainly looking for the presence of clues that make it possible to suspect a cancer: the first of them is the way the nodule is perceived on ultrasound. Quite frequently, the observed nodules appear white (they are called hyperechoic); more rarely, they appear black (anechoic). In both cases, the nodule is almost always benign. Isoechoic nodules (same shade as the rest of the thyroid) or dark grey nodules (hypoechoic nodules) can be benign or malignant. Finally, the appearance of the neighbouring thyroid lymph nodes is observed to look for a possible abnormality.

Puncture (cytological)

The results of the ultrasound examination determine whether it is necessary to perform cell punctures within the nodules to observe them under a microscope. Thus, the doctor will propose a puncture of a nodule (usually more than one cm of major axis) when associated risk factors increase the probability of malignancy: history of external radiotherapy in childhood, genetic predisposition or family disease at risk of thyroid cancer (Cowden's disease, family polyposis...), high and sustained levels of calcitonin, abnormal lymph nodes, recently enlarged nodules or those with a risk appearance (imprecise edges, hypoechoic...).

In practice, the puncture is done at the same time as the ultrasound, which guides the doctor's action. It is performed without anaesthesia because the fineness of the needle makes the sampling less painful. The examination of the cells under the microscope makes it possible to characterize the type of nodule: benign, suspect or malignant. Sometimes the sample may not be interpretable. In this case, the doctor proposes a new puncture or the removal of the suspect nodule. When the nodule is less than one cm long, simple monitoring is often recommended because the risk of cancer is low. A new ultrasound is scheduled in the following 6 to 18 months to check the benignity of the nodule.

Additional exams

Some tests are not systematically performed but are offered to certain patients according to the characteristics of their disease:

  • A thyroid scan may be indicated when the bio-logical balance shows a low TSH level. This examination, which aims to obtain a mapping of thyroid activity using a radioactive product (technetium or iodine 123), makes it possible to identify a hyperfunctional nodule, i. e. producing excess thyroid hormones;
  • A neck scanner (or cervical scanner) and an MRI (magnetic resonance imaging) are prescribed imaging procedures when the ultrasound has not sufficiently accurately described the abnormalities identified in the thyroid gland.

The extension assessment

The extension assessment determines whether the thyroid cancer cells have spread to neighbouring organs (mainly lymph nodes) or to distant organs. To do this, several additional examinations can be carried out:

  • The ENT examination is used to check the condition and mobility of the vocal cords, located just above the thyroid gland;
  • CT or MRI: a neck CT (or cervical CT) and MRI (magnetic resonance imaging) may be prescribed to assess whether thyroid cancer has spread and reached the surrounding lymph nodes;
  • PET scan: it is an imaging examination that combines a scintigraphy and a low-level radioactive marker. It allows to visualize the metabolic activity of the thyroid cells. It is mainly used in the assessment of the spread of anaplastic cancers.

Who is most likely to get thyroid cancer?

Thyroid cancer affects women more often than men. Women are two to three times more likely to develop this type of cancer than men. In addition, certain individual behaviours and characteristics increase the risk of thyroid cancer. The main risk factors identified are exposure to ionizing radiation and family history.

**Exposure to ionizing radiation

Exposure to ionizing radiation is the greatest risk factor for thyroid cancer. There is a link between the risk of thyroid cancer and the age of radiation exposure. The younger you are exposed to thyroid cancer, the higher your risk of developing it. The following are sources of ionizing radiation.

  • Radiotherapy
  • Diagnostic imaging tests

**Family history of thyroid cancer

If you have a first-degree relative who has had thyroid cancer, you are at increased risk of developing it. The increased risk may be due to certain hereditary conditions, but some families do not have a known hereditary condition.

Obesity

Research has shown that there is a link between obesity and thyroid cancer. A high body mass index (BMI) increases the risk of thyroid cancer, although the cause of this increase is not clear. Large size in adulthood Tall people are at greater risk of developing thyroid cancer, but the reason for this increased risk is unknown. There may be a link with hormone levels in childhood, adolescence or adulthood.

What are the treatments for thyroid cancer?

The choice of thyroid cancer treatment depends on the type of thyroid cancer, the stage and grade of the cancer (well differentiated or poorly differentiated) and finally, the age and general health status of the affected person. In the majority of cases, the treatment used is surgery. The surgeon removes the thyroid gland. The intervention is sometimes supplemented by radioactive iodine treatment. The overall care is generally rapid, taking place over a few months.

Surgery

In case of thyroid cancer, the first treatment is a surgical procedure: total thyroidectomy. The surgeon removes the entire gland, if necessary, from certain lymph nodes in the neck. During a total thyroidectomy, the surgeon makes an incision (cut) in the front of the neck and then removes the thyroid through this opening. Sometimes the surgeon is unable to completely remove the thyroid gland. If most of the thyroid is removed, it is called a subtotal or near-total thyroidectomy.

In some cases, only one thyroid lobe is removed. It is a lobectomy or lobisthmectomy. During a lobectomy, the surgeon makes an incision (cut) in the front of the neck. Through this opening, it removes the thyroid lobe containing the tumor and the part of the thyroid that connects the two lobes together (called the isthmus).

Radioactive iodine or iritherapy treatment

For some thyroid cancers, the surgical procedure is supplemented by a radioactive iodine treatment called iritherapy, which consists of taking radioactive iodine orally. Thyroid cells, which may remain after the procedure, whether cancerous or not, capture this circulating iodine. The rays emitted by radioactive iodine damage thyroid cells, which are eventually destroyed after several weeks or months.

Prescribed by specialists, iritherapy takes place in the hospital, in the nuclear medicine department. The patient is hospitalized in a radiation-protected room for a short time (3 to 5 days). Radioactive iodine treatment is taken from day one as a swallowable capsule. During hospitalization, it is important to drink plenty of fluids to remove radioactive iodine from the urinary tract (and intestine).

Before discharge, a scintigraphy is performed to visualize the parts of the body to which iodine 131 has been attached. This technique helps to detect and evaluate a possible spread of the disease.

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