In most areas of the world, the incidence of thyroid cancer has increased over the last few decades but related mortality has been declining.¹ Incidence rates in high-income countries are double those in low- and middle-income countries.¹

Types of thyroid cancer

Thyroid cancers are classified according to the type of cancer, its size and its tendency to spread.² Thyroid cancer is usually treatable and can be cured by surgery and, if indicated, radioactive iodine.³ There are four primary types of thyroid cancer.³

Papillary thyroid cancer is the most common type, accounting for 70–80% of cases and can occur at any age. It is a slow-growing tumor with a tendency to spread into the lymph nodes in the neck.³

Follicular thyroid cancer, comprising 10–15% of all thyroid cancers, is also slow-growing and can spread into the lymph nodes, bloodstream and more distant tissues, including the bones and the lungs.³

Medullary thyroid cancer makes up about 2% of cases, 25% of those cases run in families, and is associated with other endocrine tumors. Therefore, family members of a patient with medullary thyroid cancer should be tested for the genetic mutation.^2,3

Anaplastic thyroid cancer is the most aggressive thyroid cancer and the least likely to respond to treatment. It accounts for fewer than 2% of cases. It is a fast-growing tumor that spreads quickly and is difficult to treat.³

How is thyroid cancer diagnosed?

Thyroid cancer often develops in lumps or nodules without causing symptoms.³ Nodules are often detected incidentally, for example by CT or ultrasound scans performed for other reasons.³ The examination of the thyroid is performed by thyroid ultrasound.³ A microscopic examination of the tissue sample taken by fine-needle aspiration biopsy will show whether there are cancer cells and, in the case of diagnosis, what type of cancer they are.³ Fortunately, less than one in 10 nodules are cancerous.³

The diagnosis of thyroid cancer is a shock, and is usually followed by a flood of emotions such as sadness, fear, anger and helplessness. Learning more about your illness and the medical care available may help you overcome your fear and any feelings of helplessness. It also allows you to take an active part in the treatment process. The good news is that thyroid cancer can be treated and often cured.

Treatment of thyroid cancer

According to the American Thyroid Association, the primary treatment for all forms of thyroid cancer is the removal of part of or the entire thyroid gland by surgery.³ If the tumor has already spread into the lymph nodes in the neck or upper chest then these lymph nodes will also be removed.3 After the removal of the thyroid you will be prescribed appropriate medication. You will have to take medication on a permanent basis.³

If your tumor is large or has spread to other tissues, your doctor will probably recommend radioactive iodine (RAI) therapy after surgery.³ RAI will kill the remaining cancer cells, even those in distant tissues.³ In preparation for this treatment, you will be made hypothyroid either by stopping treatment or injecting TSH.³ The less iodine in your body, the more effective the treatment.³ You should speak to your doctor about how to balance the potential risks against the benefits of this treatment.

In patients with advanced stages of thyroid cancer, surgery and RAI treatment may not work. Your doctor then will propose radiation therapy, chemotherapy or a combination of both.³

After successful treatment, periodic follow-up examinations are necessary to be sure that the cancer has not come back. These check-ups will include physical and ultrasound examinations of the neck area and blood tests. Blood tests will show whether you are receiving the right amount of thyroxine and monitor for the presence of thyroglobulin. After thyroid removal and RAI treatment, your body should no longer produce the protein thyroglobulin (a protein produce only in the thyroid gland). If it shows up in a blood test then it is likely that your thyroid cancer has returned.³

Note: According to the American Thyroid Association, differentiated and papillary thyroid cancer patients younger than 45 years of age with a small-sized tumor or cancer confined to the thyroid gland have an excellent recovery rate.³ For these patients, the 10-year survival rate is 100%.³ For all thyroid cancer patients diagnosed in the USA between 2006 and 2012, a 5-year survival rate of 98.1% has been reported.⁴

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Date of preparation: February 2022