What is thyroid cancer?
Thyroid cancer starts in the cells of the thyroid. A cancerous (malignant) tumour is a group of cancer cells that can grow into nearby tissue and destroy it. The tumour can also spread (metastasize) to other parts of the body.
The thyroid is part of the endocrine system. It is a small gland in the front of the neck below the larynx (voice box) and near the trachea (windpipe). It has a right and left lobe, one on each side of the trachea. The lobes are joined by a thin piece of tissue called the isthmus.
Cells in the thyroid sometimes change and no longer grow or behave normally. These changes can lead to non-cancerous (benign) conditions such as hypothyroidism, hyperthyroidism, thyroid nodules or goitre.
Sometimes changes to thyroid cells can cause cancer. The most common type of thyroid cancer is papillary thyroid cancer. Follicular thyroid cancer (which includes Hurthle cell thyroid cancer) is the second most common type, but it develops much less often than papillary thyroid cancer. Medullary and anaplastic thyroid cancers can also develop, but they are less common.
Other very rare types of cancer can also start in the thyroid gland, including non-Hodgkin lymphoma and soft tissue sarcoma.