General overview

Thyroid cancer occurs in the cells of the thyroid gland, a small gland at the base of the neck. The thyroid gland produces hormones that regulate heart rate, blood pressure, body temperature, and weight. 

Thyroid cancer is asymptomatic in its early stages. However, as the disease progresses and the gland grows, symptoms such as pain and swelling in the neck appear.

There are several types of thyroid cancer. Some grow very slowly, while others can be very aggressive. Most cases of thyroid cancer can be cured without surgery.

Statistically, the incidence of thyroid cancer is increasing. This is largely due to modern diagnostic tools that detect even small thyroid cancers that might not have been detected in the past.  

Symptoms

Usually, in the early stages, thyroid cancer is asymptomatic and without any specific signs. However, as the tumor grows, the following symptoms appear:

• A lump that you feel under the skin on your neck;
• Changes in voice timbre, hoarseness;
• Difficulty swallowing;
• Neck and throat pain;
• Swollen lymph nodes in the neck.

When to see a doctor

If you are experiencing any of the above symptoms, make an appointment with an endocrinologist immediately. 

Causes

It is not known what causes thyroid cancer, but it develops when its cells undergo permanent genetic changes – mutations. Mutations allow the cell to multiply uncontrollably and rapidly. In addition, unlike normal cells, degenerated cells lose the ability to undergo programmed cell death. The accumulation of abnormal cells in the thyroid gland forms a tumor. The abnormal cells invade surrounding tissue and, through metastasis, may spread to other parts of the body.

Types of thyroid cancer

Thyroid cancer is classified into types based on the types of cells found in the tumor. The type of cancer is determined when a sample of tumor tissue is examined under a microscope. Determining the type of thyroid cancer is important for treatment and prognosis.

The types of thyroid cancer are:

• Papillary thyroid gland Cancer – The most common form of thyroid cancer, papillary thyroid cancer, arises from the follicular cells that produce and store thyroid hormones. Papillary thyroid cancer can develop at any age, but it is most common in people between the ages of 30 and 50. Doctors combine papillary and follicular thyroid cancers and call them differentiated cancers.
• Follicular thyroid cancer – Follicular thyroid cancer also arises from follicular cells. This type of cancer usually develops in people over the age of 50. Hertle cell carcinoma is a rare and potentially more aggressive type of follicular thyroid cancer.
• Anaplastic thyroid cancer – Anaplastic thyroid cancer is a rare type of cancer that begins in the follicular cells. It grows quickly and is difficult to treat. Anaplastic thyroid cancer usually occurs in people over the age of 60.
• Medullary thyroid cancer – Medullary thyroid cancer begins in the C cells of the thyroid gland, which produce the hormone calcitonin. Elevated levels of calcitonin in the blood may indicate early stages of medullary thyroid cancer. Some genetic syndromes increase the risk of medullary thyroid cancer, although such genetic links are rare.
• Other rare species – Rare tumors that develop in the thyroid gland can be lymphoma and sarcoma. Lymphoma develops from immune cells in the thyroid gland, while sarcoma develops from the connective tissue of the thyroid gland.

Risk factors

Risk factors for developing thyroid cancer include:

• Female gender – Thyroid cancer is more common in women than in men;
• Exposure to high levels of radiation – Radiation therapy to the head and neck increases the risk of thyroid cancer;
• Certain inherited genetic syndromes – Genetic syndromes that increase the risk of thyroid cancer include hereditary medullary thyroid cancer, multiple endocrine neoplasia, Cowden syndrome, and familial adenomatous polyposis.

Thyroid cancer recurrence

Despite treatment, thyroid cancer can recur. Moreover, it is possible for it to recur even after the thyroid gland has been removed. A recurrence occurs when microscopic cancer cells spread beyond the thyroid gland before it is removed.

Thyroid cancer can recur:

• In the lymph nodes of the neck;
• A small portion of thyroid tissue remaining during surgery;
• In other areas of the body, such as the lungs and bones.

Recurrent thyroid cancer is treatable. Your doctor may periodically order blood tests or thyroid scans to check for signs of cancer recurrence.

Prevention

Doctors don't know exactly what causes most cases of thyroid cancer, so there is almost no way to prevent thyroid cancer in people who are at average risk for the disease.

Prevention in high-risk groups

Adults and children who have an inherited gene mutation that increases the risk of medullary thyroid cancer may be considered for thyroid surgery, a prophylactic thyroidectomy, to prevent cancer. 

To reduce your risk of thyroid cancer, discuss any options with a genetic counselor, who can educate you about your cancer risk and treatment options.