Thyroid Cancer

Thyroid cancer is a malignant tumour arising from the cells of the thyroid gland at the front of the lower neck. Most of its types are slow-growing. It usually presents as a swelling noticed in the neck or as a nodule found on ultrasound.

What is thyroid cancer?

The thyroid gland is made up of follicular cells, which produce thyroid hormone, and C cells, which produce a hormone involved in calcium balance. Cancer is classified into types according to the cell from which it arises:^1,2

• Papillary thyroid cancer: The most common type; it usually grows slowly and tends to spread first to the lymph nodes of the neck.²
• Follicular thyroid cancer: The second most common type, arising from follicular cells; it tends to spread through the bloodstream rather than to the lymph nodes.
• Medullary thyroid cancer: Arises from C cells; some cases run in families.
• Anaplastic thyroid cancer: A rare, rapidly progressing type that requires a different treatment approach.

The papillary and follicular types are together called “well-differentiated” thyroid cancers and account for the large majority of thyroid cancers.^1,2

Risk factors

In most patients the exact cause is unknown. Radiation to the neck region in childhood, a family history of thyroid cancer, certain inherited syndromes and female sex are counted among the risk factors. However, it can also occur in people with no risk factors at all.¹

Symptoms

In the early period it usually causes no symptoms. Symptoms that may occur:¹

• A firm swelling at the front of the neck that moves on swallowing
• Enlarged lymph nodes at the sides of the neck
• Hoarseness that does not go away
• Difficulty swallowing or shortness of breath

Diagnosis and staging

The diagnosis is made by ultrasound and fine-needle aspiration biopsy. Ultrasound assesses the features of the nodule and the lymph nodes of the neck; the biopsy determines the type of cells. When needed, computed tomography or magnetic resonance imaging is used to examine the extent of the disease; if the medullary type is suspected, the calcitonin level in the blood is measured. The disease is classified from stage I to stage IV according to the size of the tumour, whether it has extended beyond the gland, involvement of lymph nodes and distant organs, and the patient’s age. The stage determines the treatment plan and the frequency of follow-up.^1,3

Treatment

The main treatment is surgery. Depending on the size and extent of the tumour, one lobe (lobectomy) or the whole gland (total thyroidectomy) is removed; if the lymph nodes of the neck are involved or suspected to be, they are cleared as well (neck dissection). After surgery, radioactive iodine treatment may be given to selected patients to destroy the remaining thyroid tissue and any possible microscopic disease. When the whole gland is removed, thyroid hormone medication is taken for life. Drugs may also be given to prevent the body from making thyroid-stimulating hormone (TSH), a hormone that can increase the chance that thyroid cancer will grow or come back. Radiotherapy and targeted drugs are considered in advanced-stage disease or disease that does not respond to iodine.^1,3,4

Follow-up

Regular follow-up after treatment allows any recurrence to be detected early. Follow-up uses neck ultrasound, thyroid hormone levels and tumour markers (thyroglobulin for the papillary and follicular types, calcitonin for the medullary type). The intervals between follow-up visits lengthen over time, but follow-up continues for many years.^3,4

When should you see a doctor?

If you notice a new swelling in your neck, an enlarging lymph node or hoarseness that has persisted for a few weeks, it is advisable to see a doctor for assessment.