About Thyroid Cancer

Thyroid cancer stems from the cells of the thyroid, which is a butterfly-shaped gland located at the front of the neck, just below the larynx (voice box) and on top of the central trachea (windpipe). The thyroid is an important part of the endocrine system, a group of specialized glands and cells whose role is to produce hormones.

The thyroid gland’s main function is to produce hormones that play a key role in the digestive system, keep the nervous system working normally, develop the brain in children, and control body temperature, heart rate, blood pressure, and breathing.

There are cancerous and non-cancerous, or benign, lesions that can affect the thyroid.

Benign lesions include thyroid nodules, which are asymptomatic lumps or growths on the thyroid. Usually, a fine needle aspiration and a biopsy are performed to diagnose and distinguish these from cancer. 95% of these nodules are benign, and not a cause for concern. Another benign thyroid lesion is a goiter, which is an enlargement of the gland. (1)

Sometimes, the cells of the thyroid can mutate and begin growing in an unregulated and abnormal manner; this is referred to as thyroid cancer.

Thyroid cancer is a malignant tumour, meaning it can spread, or metastasize, to other sites in the body. Possible sites of metastasis include the lymph nodes, the lungs, and bone. It can also spread to other structures in the neck, such as the trachea, esophagus, blood vessels, muscles, and nerves.


Types of thyroid cancer

Thyroid cancer is typically one of two types: papillary carcinoma or follicular carcinoma. Papillary carcinoma is the most common type, representing more than 80% of cases. This cancer grows from the follicular cells of the thyroid, and typically grows slowly and responds well to treatment. Follicular carcinoma is much less common, representing less than 10% of cases. Much like papillary carcinoma, this cancer originates in the follicular cells. In most cases, it also grows slowly and has a fairly good prognosis.

Other less common forms of thyroid cancer include:

  • Medullary carcinoma
    • This cancer makes up about 5% of thyroid cancers, and most often develops in the 50-60 year age group. It originates in the parafollicular cells of the thyroid, and is sometimes associated with a hereditary neuroendocrine condition called Multiple Endocrine Neoplasia 2, or MEN2. However, many cases of medullary carcinoma are sporadic, meaning they happen by chance.
  • Poorly differentiated carcinoma
    • This cancer represents about 2% of all thyroid cancers. Much like papillary and follicular carcinoma, it stems from the follicular cells. It is an aggressive cancer, meaning it grows and spreads quickly. It is typically diagnosed after it has already spread to other parts of the body, and has a fairly high chance of recurrence after treatment.
  • Anaplastic carcinoma
    • Anaplastic carcinoma accounts for less than 2% of all thyroid cancer cases. It is similar to poorly differentiated carcinoma in most regards, as it is aggressive and usually diagnosed after having spread to other tissues. It will sometimes occur at the same time as other thyroid cancers, so some experts believe it comes from a papillary or follicular carcinoma. It is most commonly found in older people.
  • Thyroid lymphoma
    • A very rare form of thyroid cancer originating in the lymphocytes.
  • Soft tissue sarcoma
    • A very rare form of thyroid cancer which begins in soft tissue cells.


Information taken from Canadian Cancer Society unless otherwise indicated.

(1) “Thyroid Cancer Treatment”, National Cancer Institute. https://www.cancer.gov/types/thyroid/patient/thyroid-treatment-pdq


Risk Factors


Signs and Symptoms