Thyroid cancer is a disease in which malignant (cancer) cells form in the tissues of the thyroid gland.
The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin.
Anatomy of the thyroid and parathyroid glands. The thyroid gland lies at the base of the throat near the trachea. It is shaped like a butterfly, with the right lobe and left lobe connected by a thin piece of tissue called the isthmus. The parathyroid glands are four pea-sized organs found in the neck near the thyroid. The thyroid and parathyroid glands make hormones.
The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones do the following:
Control heart rate, body temperature, and how quickly food is changed into energy (metabolism).
Control the amount of calcium in the blood.
There are four main types of thyroid cancer:
Papillary thyroid carcinoma
- This is the most common form of thyroid cancer. 70% of thyroid cancers are papillary.
- It usually presents between 35 and 40 years of age and is three times more common in women.
- Most often, it presents as micropapillary thyroid carcinoma (<1 cm in size) with an excellent long-term prognosis.
- It tends to spread locally in the neck, compressing the trachea and possibly involving the recurrent laryngeal nerve.
- Metastases most often occur in lung and bone.
Follicular thyroid carcinoma
- This is the second most common form of thyroid cancer at about 10%.
- It tends to occur in areas of low iodine.
- It is three times more common in women and most often presents between 30 and 60 years of age.
- It may infiltrate the neck, as does PTC, but it has a greater propensity to metastasise to lung and bones.
Medullary thyroid carcinoma (a form of follicular thyroid carcinoma)
- Medullary thyroid cancer arises from the parafollicular calcitonin-producing C cells of the thyroid and accounts for between 5% and 8% of all thyroid malignancies.
- Female preponderance is less marked.
- Malignant transformed C cells produce and secrete large amounts of peptides, including carcinoembryonic antigen (CEA) and calcitonin and so elevated serum calcitonin is a marker of the presence of MTC or metastatic MTC after surgery.
- Up to 75% of MTC cases occur sporadically. The hereditary form of MTC (23% of cases) shows an autosomal dominant pattern of transmission.
- Familial MTC arises as part of multiple endocrine neoplasia (MEN) syndrome type 2A or 2B or familial MTC (FMTC).
- Prognostic factors that predict adverse outcome include calcitonin doubling time, advanced age at diagnosis, extent of the primary tumour, nodal disease and distant metastases.
Hürthle cell carcinoma
- Hürthle cell carcinoma accounts for about 3-10% of all differentiated thyroid cancers.
- They are composed of 75-100% Hürthle cells.
- There is a female preponderance.
- It may present from 20-85 years of age but most often between the ages of 50-60 years.
- It is impossible to distinguish benign from malignant tumours on fine-needle aspiration (FNA).
- Surgical excision is the main treatment. Other treatments include postoperative radioactive iodine-131 treatment, levothyroxine (T4) and external radiotherapy.
- Hürthle cell carcinomas behave more aggressively than other well-differentiated thyroid cancers with a higher incidence of metastasis and a lower survival rate.
Anaplastic thyroid carcinomas
- Anaplastic thyroid carcinoma (ATC) is the most aggressive thyroid tumour and one of the most aggressive cancers in humans.
- ATC arises from the follicular cells of the thyroid gland but does not retain any of the biological features of the original cells, such as uptake of iodine and synthesis of thyroglobulin.
- The peak incidence is in the sixth to seventh decades (mean age at diagnosis 55-65 years) and the prevalence is very low (<2% of all thyroid tumours).
- In most cases, ATC develops from a pre-existing well-differentiated thyroid tumour, which has undergone additional mutational events.
- The clinical diagnosis is usually easy with a large, hard mass invading the neck and causing compression (dyspnoea, cough, vocal cord paralysis, dysphagia and hoarseness). Almost 50% of the patients present with distant metastases, mostly in the lungs but also in the bones, liver and brain.
- The mean overall survival is often less than six months, whatever treatment is performed.
Age, gender, and exposure to radiation can affect the risk of developing thyroid cancer.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for thyroid cancer include the following:
- Being between 25 and 65 years old.
- Being female.
- Being exposed to radiation to the head and neck as a child or being exposed to atomic bomb radiation. The cancer may occur as soon as 5 years after exposure.
- Having a history of goiter (enlarged thyroid).
- Having a family history of thyroid disease or thyroid cancer.
- Having certain genetic conditions such as familial medullary thyroid cancer (FMTC), multiple endocrine neoplasia type 2A syndrome, and multiple endocrine neoplasia type 2B syndrome.
- Being Asian.
Medullary thyroid cancer is sometimes caused by a change in a gene that is passed from parent to child.
The genes in cells carry hereditary information from parent to child. A certain change in a gene that is passed from parent to child (inherited) may cause medullary thyroid cancer. A test has been developed that can find the changed gene before medullary thyroid cancer appears. The patient is tested first to see if he or she has the changed gene. If the patient has it, other family members may also be tested. Family members, including young children, who have the changed gene can decrease the chance of developing medullary thyroid cancer by having a thyroidectomy (surgery to remove the thyroid).
Possible signs of thyroid cancer include a swelling or lump in the neck.
Thyroid cancer may not cause early symptoms. It is sometimes found during a routine physical exam. Symptoms may occur as the tumour gets bigger. Other conditions may cause the same symptoms. Check with your doctor if you have any of the following problems:
- A lump in the neck.
- Trouble breathing.
- Trouble swallowing.
Tests that examine the thyroid, neck, and blood are used to detect (find) and diagnose thyroid cancer.
The following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or swelling in the neck, voice box, and lymph nodes, and anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- Laryngoscopy: A procedure in which the doctor checks the larynx (voice box) with a mirror or with a laryngoscope. A laryngoscope is a thin, tube-like instrument with a light and a lens for viewing. A thyroid tumour may press on vocal cords. The laryngoscopy is done to see if the vocal cords are moving normally.
- Blood hormone studies: A procedure in which a blood sample is checked to measure the amounts of certain hormones released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it. The blood may be checked for abnormal levels of thyroid-stimulating hormone (TSH). TSH is made by the pituitary gland in the brain. It stimulates the release of thyroid hormone and controls how fast follicular thyroid cells grow. The blood may also be checked for high levels of the hormone calcitonin and antithyroid antibodies.
- Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances, such as calcium, released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
- Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later. This procedure can show the size of a thyroid tumour and whether it is solid or a fluid -filled cyst. Ultrasound may be used to guide a fine-needle aspiration biopsy.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
- Fine-needle aspiration biopsy of the thyroid: The removal of thyroid tissue using a thin needle. The needle is inserted through the skin into the thyroid. Several tissue samples are removed from different parts of the thyroid. A pathologist views the tissue samples under a microscope to look for cancer cells. Because the type of thyroid cancer can be hard to diagnose, patients should ask to have biopsy samples checked by a pathologist who has experience diagnosing thyroid cancer.
- Surgical biopsy: The removal of the thyroid nodule or one lobe of the thyroid during surgery so the cells and tissues can be viewed under a microscope by a pathologist to check for signs of cancer. Because the type of thyroid cancer can be hard to diagnose, patients should ask to have biopsy samples checked by a pathologist who has experience diagnosing thyroid cancer.
Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery) and treatment options depend on the following:
- The age of the patient.
- The type of thyroid cancer.
- The stage of the cancer.
- The patient's general health.
- Whether the patient has multiple endocrine neoplasia type 2B (MEN 2B).
- Whether the cancer has just been diagnosed or has recurred (come back).
For more information on Thyroid Cancer click here
To get information from the Australian HealthDirect website, click here
This link is to the National Cancer Institute (NCI) cancer website in the United States. There may be references to drugs and clinical trials that are not available here in Australia.
Information has also been sourced from patient.info
For information courtesy of Cancer Australia, please click here