Definition: Thyroid cancer is a cancer that starts in the thyroid gland. The thyroid gland is located inside the front of your lower neck.
Thyroid cancer can occur in people of any age.
Radiation increases the risk of developing thyroid cancer. Exposure may occur from:
- Radiation therapy to the neck (especially in childhood)
- Radiation exposure from nuclear plant disasters
Other risk factors are a family history of thyroid cancer and chronic goiter (enlarged thyroid).
There are several types of thyroid cancer:
- Anaplastic carcinoma (also called giant and spindle cell cancer) is the most dangerous form of thyroid cancer. It is rare, and spreads quickly.
- Follicular tumour is more likely to come back and spread.
- Medullary carcinoma is a cancer of non-thyroid cells that are normally present in the thyroid gland. This form of thyroid cancer tends to occur in families.
- Papillary carcinoma is the most common type, and it usually affects women of childbearing age. It spreads slowly and is the least dangerous type of thyroid cancer.
Symptoms vary depending on the type of thyroid cancer, but may include:
- Difficulty swallowing
- Enlargement of the thyroid gland
- Hoarseness or changing voice
- Neck swelling
- Thyroid lump (nodule)
Your health care provider will perform a physical exam. This may reveal a lump in the thyroid, or swollen lymph nodes in the neck.
The following tests may be done:
- Calcitonin blood test to check for medullary thyroid cancer
- Laryngoscopy (looking inside the throat using a mirror or flexible tube called a laryngoscope placed through the mouth)
- Thyroid biopsy
- Thyroid scan
- TSH, free T4 (blood tests for thyroid function)
- Ultrasound of the thyroid
- CT scan of the neck (to determine the extent of the cancerous mass)
- PET scan
Treatment depends on the type of thyroid cancer. Treatment of most thyroid cancer types is effective if diagnosed early.
Surgery is most often done. The entire thyroid gland is usually removed. If your provider suspects that the cancer has spread to lymph nodes in the neck, these will also be removed.
Radiation therapy may be done with or without surgery. It may be performed by:
- Aiming external beam (x-ray) radiation at the thyroid
- Taking radioactive iodine by mouth
After treatment for thyroid cancer, you must take thyroid hormone pills for the rest of your life. The dosage is usually slightly higher than what your body needs. This helps keep the cancer from coming back. The pills also replace the thyroid hormone your body needs to function normally.
You can ease the stress of illness by joining a cancer support group. Sharing with others who have common experiences and problems can help you not feel alone.
Complications of thyroid cancer may include:
- Injury to the voice box and hoarseness after thyroid surgery
- Low calcium level from accidental removal of the parathyroid glands during surgery
- Spread of the cancer to the lungs, bones, or other parts of the body
Call your provider if you notice a lump in your neck.
There is no known prevention. Awareness of risk (such as previous radiation therapy to the neck) can allow earlier diagnosis and treatment.
Sometimes, people with family histories and genetic mutations related to thyroid cancer will have their thyroid gland removed to prevent cancer.
National Cancer Institute website. Thyroid cancer treatment (adult) (PDQ) – health provisional version. www.cancer.gov/cancertopics/pdq/treatment/thyroid/HealthProfessional. Updated February 1, 2018. Accessed March 22, 2018.
Smith PW, Hanks LR, Salomone LJ, Hanks JB. Thyroid. In: Townsend CM Jr, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 20th ed. Philadelphia, PA: Elsevier; 2017:chap 36.
Thompson LDR. Malignant neoplasms of the thyroid gland. In: Thompson LDR, Bishop JA, eds. Head and Neck Pathology. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 25.