What Is Thyroid Cancer? What Causes Thyroid Cancer?
Thyroid cancer, or cancer of the thyroid is cancer of the thyroid gland, which is located in the front of the neck - the thyroid gland produces hormones which regulate normal body metabolism, heart rate, blood pressure, body temperature and weight. It is not a common type of cancer, although its incidence is rising.
There are various types of thyroid cancer:
- Papillary thyroid cancer - accounts for about 80% of all cases. It is most commonly diagnosed in patients aged between 30 and 50 years of age.
- Follicular thyroid cancer - accounts for about 11% of all cases. It is most commonly diagnosed in individuals aged 50 years or more.
- Medullary thyroid cancer - accounts for about 4% of all cases. Some patients have a genetic fault (mutation) and commonly have cancer in other glands as well.
- Anaplastic thyroid cancer - accounts for about 1% or 2% of all cases. It is most commonly diagnosed in patients over 60 years of age. It is an aggressive cancer.
- Thyroid lymphoma - accounts for about 1% to 2% of all cases. This rare cancer typically affects patients aged over 70 years. It begins in the immune system cells in the thyroid gland.
Thyroid cancer affects both men and women, but women are more likely to get it (75% of all cases).
According to the CDC (Centers for Disease Control and Prevention), USA, approximately 37,000 Americans are diagnosed with thyroid cancer annually. The National Health Service (NHS), UK, informs that thyroid cancer accounts for about 1% of all cancers diagnosed in the United Kingdom. In England and Wales (not including Scotland or Northern Ireland) approximately 1,200 new cases are diagnosed each year.
What is the thyroid gland?This is a gland that all mammals (humans are mammals) have. It makes and stores hormones that control our blood pressure, body temperature, heart rate and metabolism (speed at which food is converted into energy; the rate of chemical reactions in the body). The function of every cell in our body depends on these hormones.
The thyroid gland lies below the Adam's apple, in the lower part of the neck. It has a butterfly shape, with two lobes (wings) attached to each other by a middle part.
We need iodine, which we get from food, for the thyroid gland to function properly - for it to make its hormones.
The thyroid gland has:
- follicular cells which produce thyroxine (T4) and triiodothyronine (T3) - these two hormones affect heart rate, body temperature and energy levels.
- C cells which produce calcitonin - this hormone helps control calcium blood levels. We need calcium in our blood for strong bones and to prevent blood clots.
What are the symptoms of thyroid cancer?A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.
Thyroid cancer typically develops very slowly and will not usually present any symptoms during its early stages. Examples of symptoms include:
- Initially, a small, painless lump in the neck. Under 5% of these nodules are found to be malignant (cancerous). However, if the patient is under 20, the chances of malignancy are higher.
- There may be pain in the neck and throat later on.
- Hoarseness, or problems speaking with a normal voice.
- The lymph nodes in the neck are swollen.
- There may be some breathing difficulties.
- Usually, thyroid function is fine. However, if the tumor is large, the thyroid may be overactive (hyperthyroidism) or underactive (hypothyroidism).
What are the causes of thyroid cancer?What is cancer? - cancer is a class of diseases characterized by out-of-control cell growth. Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors (except in the case of leukemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.
More dangerous, or malignant, tumors form when two things occur:
- a cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
- that cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.
In 2007, cancer claimed the lives of about 7.6 million people in the world. Physicians and researchers who specialize in the study, diagnosis, treatment, and prevention of cancer are called oncologists.
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.
Papillary and follicular thyroid cancers spread much more slowly than the other, rarer types.
What are the risk factors for thyroid cancer?
- Radiation exposure - especially in early childhood, increases the risk of developing thyroid cancer. This could be due to an all-nuclear fallout that occurs after a nuclear explosion, or radiation treatment for medical conditions/diseases when radiation risks were not properly understood (before the early 1960s).
- Gender - three-quarters of all patients with thyroid cancer are female. This does not mean a woman will get thyroid cancer, which is a rare disease.
- Some health conditions/diseases - people with the following conditions/diseases have a higher risk of developing thyroid cancer: Hashimoto's thyroiditis, Cowden's syndrome, thyroid adenoma and familial adenomatous polyposis.
- Genetics - some inherited conditions increase the risk of developing medullary thyroid cancer. Approximately one quarter of individuals who develop medullary thyroid cancer have and abnormal gene.
- Family history - individuals with a family history of goiter (thyroid gland enlargement) have a higher risk of developing thyroid cancer.
How is thyroid cancer diagnosed?The doctor, often a GP (general practitioner, primary care physician) at first, will examine the patient's neck and throat and ask questions regarding symptoms. Blood test - called a thyroid function test, measures specific blood hormone levels. If thyroxine and triiodothyronine levels are too high, the thyroid gland is overactive for some reason. If thyroid stimulating hormone (TSH) levels are too high, it means the thyroid gland is underactive - TSH is produced by the pituitary gland in order to stimulate the thyroid gland.
Fine-needle aspiration cytology (biopsy) - a small needle passes into the swelling in the patient's neck and a sample of cells is removed and then examined under a microscope. The biopsy will determine whether the lump is cancerous, and what type of cancer it is.
Imaging scans - the doctor may also order a CT or MRI scan.
Surgery (biopsy) - if the needle aspiration is inconclusive, a small sample of the thyroid gland may need to be surgically removed and examined.
What is the treatment for thyroid cancer?The doctor may recommend surgery, radioactive iodine and/or radiotherapy. In most cases, especially during the early stage of the cancer, treatment is effective and the thyroid cancer is cured.
Surgery - common surgeries include:
- Thyroidectomy - the surgical removal of part or all of the thyroid gland. During this operation, the surgeon may also remove the lymph nodes in the neck.
- Lobectomy (hemithyroidectomy) - the surgical removal of a lobe (one of the wings of the thyroid gland).
- Tracheostomy - making an incision on the front of the neck and opening a direct airway through an incision in the trachea (windpipe), allowing the patient to breathe.
There is a risk of damage to the vocal cords from surgery, which can change the patient's voice (hoarseness). There may also be breathing difficulties. If the parathyroid glands, which help regulate blood calcium levels, are affected, the patient may need to take calcium supplements - usually the parathyroid glands recover after some time.
Thyroid hormone therapy - if the thyroid gland is completely or partially removed, the patient will need to take replacement hormone tablets for the rest of his/her life. The patient will need regular blood tests to make sure hormone levels are right.
Radioactive iodine - after surgery the patient may receive a course of radioactive iodine therapy, which is aimed at preventing thyroid cancer recurrence (stops the cancer form coming back). After treatment patients will be on a low-iodine diet. Pregnant women should not receive radioactive iodine treatment.
External radiation therapy (radiotherapy) - usually only used for medullary or anaplastic thyroid cancers.
Chemotherapy - usually only used to treat anaplastic thyroid cancer that has metastasized (spread to other parts of the body).