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Thyroid cancer

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What is thyroid cancer?

Thyroid cancer is a malignant tumour that starts in the cells of the thyroid. Malignant means that it can spread, or metastasize, to other parts of the body.

The thyroid is part of the endocrine system. It is a small gland at the front of your neck below the larynx, or voice box. It has 2 parts called lobes. Each lobe sits on one side of the trachea, or windpipe. The lobes are connected by a thin piece of tissue called the isthmus. The thyroid is made up of 2 types of cells:

  • Follicular cells make the thyroid hormones. These hormones help control body functions, including heart rate, blood pressure, body temperature and weight.
  • C cells are also called parafollicular cells. They make the hormone calcitonin, which helps control the levels of calcium and phosphate in your blood.

Cells in the thyroid sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, conditions such as hypothyroidism, hyperthyroidism, thyroiditis and thyroid nodules.

In some cases, changes to different types of thyroid cells can cause thyroid cancer. The most common type of thyroid cancer is called papillary thyroid cancer, which makes up about 70% of all thyroid cancers.

Follicular thyroid carcinoma is the second most common type of thyroid cancer. Less commonly, changes to thyroid cells may develop into anaplastic thyroid cancer. Medullary thyroid carcinoma is another type of thyroid cancer. It starts in C cells.

Rare types of thyroid cancer can also develop. These include lymphoma, squamous cell carcinoma and sarcoma.

Diagram of the location and structure of the thyroid gland

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