General Information / Anatomy / Function / Statistics

• Thyroid gland is located low in the neck, between the thyroid cartilage (Adam's apple) and the collar bones
• Dumbbell shaped, consists of three sections; two lobes, one on either side of the windpipe, and the connecting section called the "isthmus"
• It is part of the endocrine system
• It produces hormones that regulate metabolism, particularly thyroxine (T4) and to a lesser extent triiodothyronine (T3)
• An enlargement of the thyroid gland is called a goiter
• Occasionally due to deficiency of iodine in the diet
• A benign condition
• Patients with goiter or a family history of goiter may have a risk of developing cancer of the thyroid if the cause of the goiter is not treated
• There are 4 main types of thyroid cancer:
• Papillary
• Follicular
• Medullary
• Anaplastic
• Thyroid cancer accounts for only 1% of invasive cancers
• Two parathyroid glands lie at the edge of each lobe of the thyroid, together with C-cells in the thyroid, the parathyroids control calcium metabolism
• For statistics, please click here.

Symptoms / Signs

• Painless lump in the neck
• Enlarged thyroid gland - or collar getting tight
• May present with lymph node metastasis
• Late symptoms - due to local growth and invasion of adjacent tissues may include:
  • Difficulty breathing and swallowing
  • Hoarseness
  • Metastasis to other sites

Etiology / Carcinogens / Risks

• Occurs most often in those between 25 and 65 years of age
• Radiation exposure to the neck area in infancy or childhood usually to the thymus gland. This form of treatment was rare after 1950. Induction period (delay time from time of radiation to time of developing thyroid cancer) is 15-30 years.
• Thyroid pathology more common in females but when a lump appears in a male, it has a greater chance of being malignant
• Apparently benign solitary nodule that doesn't shrink after 3-4 months of thyroxine should be surgically treated
• History of goiter. This is a rare cause of thyroid cancer which is becoming increasingly less important.
• Some medullary carcinomas are hereditary and the families of patients may be screened by measuring blood calcitonin levels
• People with chronic TSH (thyroid-stimulating hormone) elevation have increased risk
• Note: It is highly unlikely that thyroid cancer will be caused by the dose of X-rays used for diagnostic procedures. There is a small risk after higher dose treatment of lymphoma or head and neck cancer, but the latent period will be at least 15 years.

Prevention

• Include adequate amount of iodine in the diet

Diagnosis / Staging / Grading Types

• Frequently found during regular physical check-up
• Ultrasound examination with needle biopsy may give diagnosis
• Thyroid scan with radioactive iodine sometimes helpful
• People with enlarged thyroid should have thyroid function tests and an ultrasound scan

Staging

Types

Papillary carcinoma

• Most common form with 80% overall survival at 10 years
• May remain localized for years with high rate of cure
• May spread to lymph nodes but this does not worsen outlook
• May develop distant metastases, but this is rare

Follicular carcinoma

• Follicular cancers are most likely to spread by the bloodstream to lungs or bone
• Often treated with radioactive iodine since this tumour is most likely to capture radioactive iodine

Medullary carcinoma

• Is more aggressive than papillary and follicular cancers
• It may spread to the lymph glands or by the bloodstream
• It often produces the hormone calcitonin, which is a useful marker
• Usually only occurs on only one side of the thyroid

Anaplastic carcinoma

• Noted for fast growth and early spread
• Occurs in middle aged and elderly patients
• Usually more advanced at the time of diagnosis and may not be possible to remove surgically, often treated with radiation therapy alone
• Anaplastic cancers are the most aggressive thyroid cancers, only a small proportion of patients are cured

Treatment

Surgery

• The treatment of choice for all localized thyroid cancers
• Often, surgical removal is all that is required
• Minimum operation is to remove the involved lobe, removal of the isthmus and much of the other lobe may also be required
• Thyroid operations have some risk of damage to the nerves in the neck that supply the larynx (voice box)

Radioactive Iodine Therapy

• May be used to destroy any remaining thyroid tissue or to treat recurrent disease or metastases
• Only papillary and follicular cancers will take up iodine and only 50% or less of these tumours will take up iodine in sufficient quantities to be therapeutically useful
• Patient has to be off thyroxine for at least 4 weeks and T3 for at least 2 weeks before an iodine scan or treatment will work
• Radioactive iodine is given as a drink, patients have to stay in hospital for a few days after a therapeutic dose to allow the radioactivity to fall to safe levels. Scans are done as outpatients
• Side effects include possible temporary bone marrow suppression, inflammation of salivary glands, nausea and vomiting

External Beam Radiation

• Used when high risk of recurrence in the neck or thyroid bed, usually if tumour doesn't take up iodine
• Usually 4 week course
• Side effects - transient reddening of skin, sore throat and laryngitis

Chemotherapy

• At present chemotherapy has only a limited role in the treatment of thyroid cancer

Thyroxine Replacement

• Lifelong thyroxine therapy is essential. The thyroxine replaces what the thyroid should produce. In addition, slightly higher doses than are necessary for replacement alone appears to reduce the risk of tumour recurrence.

Prognosis

• Most patients with papillary and follicular carcinomas will not die of thyroid cancer
• Anaplastic carcinoma has a less favourable prognosis
• Medullary cancer lies in between being more serious than papillary and follicular tumours, but more likely to be cured than anaplastic carcinoma

Revised August 1996

March 2007  We are currently reviewing and updating these pages.  If you have any questions about your cancer and its treatment, please discuss with your oncologist or physician.  Thank you.