What is thyroid cancer?

Thyroid cancer starts in the cells of the thyroid. The thyroid is a small gland at the front of your neck below the voice box (larynx). It is shaped like a butterfly. It has 2 parts (called lobes), one on each side of the windpipe (trachea). The lobes are connected by a thin piece of tissue called the isthmus.

The thyroid makes hormones that help your body work the way it is supposed to.

• Thyroxine (T4) and triiodothyronine (T3) are hormones that help control body functions, including your heart rate, blood pressure, body temperature and weight. To make T3 and T4, the thyroid needs iodine. It gets iodine from the food you eat.
• Calcitonin helps control the level of calcium and phosphate in your blood.

There are 4 main types of thyroid cancer. Each type looks different under a microscope, behaves differently and is treated differently.

• Papillary carcinoma is the most common type of thyroid cancer. It grows slowly.
• Follicular carcinoma grows slowly, but grows faster than papillary carcinoma.
• Medullary thyroid cancer is a rare type of thyroid cancer that grows slowly and causes high levels of calcitonin.
• Anaplastic thyroid cancer is also a rare type of thyroid cancer. It tends to grow and spread very quickly.