The body is made up of cells that grow and die in a controlled way. Sometimes, cells keep dividing and growing without normal controls, causing an abnormal growth called a tumour. A tumour can be benign (harmless), premalignant (if left untreated, may lead to cancer) or malignant (progressively worsens and can result in death). Cancer is a malignant tumour.
Thyroid cancer is a type of cancer of the thyroid gland, which is a butterfly-shaped gland at the base of the neck. The thyroid gland is a part of an intricate network of glands called the endocrine system, which is responsible for coordinating many of the body's activities. When the thyroid is its normal size, you can’t feel it.
Thyroid cancer occurs when cells in the thyroid gland undergo rapid multiplication due to genetic mutations or certain environmental factors. The resultant accumulation of abnormal thyroid cells forms a tumour. There are different types of thyroid cancer that can be diagnosed with the help of various diagnostic tests. The treating doctor can give more information about the type of thyroid cancer diagnosed in the patient.
The exact cause of thyroid cancer is not clear; however, factors that may increase the risk of thyroid cancer are as follows:
- Gender: Thyroid cancer is more common in women than in men.
- Age: In women, thyroid cancer is usually diagnosed between 40 to 50 years of age. Men are usually diagnosed between 60 to 70 years of age.
- Genetic factors: Damage to certain genes (due to inherited or environmental changes) increases the risk of thyroid cancer. Certain genetic conditions may also increase the risk of thyroid cancer.
- Radiation exposure: Radiation therapy to the head and neck regions increases the risk of thyroid cancer.
- Family history: Thyroid cancer can sometimes run in families.
Symptoms are rare in the early stage of the disease. As thyroid cancer grows, it may cause the following:
- A swelling or lump in the neck, which is usually fast growing; this could also be felt through the skin.
- Increasing hoarseness of voice.
- Difficulty in swallowing.
- Pain in the front area of the neck.
- Swollen lymph nodes in the neck (lumpy swelling in the neck).
Medical history and examination: Checking the neck region to feel for any lump and/or changes in the thyroid, such as thyroid nodules. Checking all medical history of past exposure to radiation and family history of thyroid tumours could help in the diagnosis.
Blood tests: These help to determine if the thyroid gland is functioning normally. Thyroid-stimulating hormone (TSH) levels in the blood are useful in the diagnosis of thyroid cancer. The TSH is higher in patients with thyroid cancer, and higher TSH has also been associated with extension of the cancer outside the thyroid gland.
Ultrasound imaging: Ultrasound uses high-frequency sound waves to create images of the thyroid gland. The appearance of the thyroid gland on the ultrasound helps to determine whether a thyroid nodule is solid or filled with fluid as solid nodules are more likely to be cancerous.
Radioiodine scan or radioactive iodine uptake scan: The test measures the amount of radioactive iodine (taken by mouth) that accumulates in the thyroid gland. These scans are used to help determine if the lump in the neck is thyroid cancer and also show if it has spread.
Biopsy: A ‘fine-needle biopsy’ is usually performed. During this procedure, a long, thin needle is inserted through the skin and into the thyroid nodule. This is guided by ultrasound imaging to precisely guide the needle into the nodule. Samples of suspicious thyroid tissue are collected and are analysed in the laboratory to look for cancer cells.
Magnetic resonance imaging (MRI): MRI scans use magnets instead of radiation to create detailed cross-sectional images of your body. MRI can be used to look for cancer in the thyroid, or cancer that has spread to nearby or distant parts of the body. MRI can provide very detailed images of soft tissues such as the thyroid gland. But, usually, ultrasound is the first choice for looking at the thyroid.
The treatment usually depends on the type and stage of the cancer. These include removal of the tumour (surgery), killing the cancer cells with drugs (chemotherapy) or radiation (radiotherapy). Depending on the size and spread of the cancer, treatment can include any of these therapies or a combination.
Surgery: Operations used to treat thyroid cancer include the following:
Removing all or most of the thyroid (thyroidectomy): An operation to remove the thyroid gland might involve removing all the thyroid tissue (total thyroidectomy) or most of the thyroid tissue (near-total thyroidectomy).
Removing a portion of the thyroid (thyroid lobectomy): During a thyroid lobectomy, half of the thyroid gland is removed.
Removing lymph nodes in the neck (lymph node dissection): When removing the thyroid, the surgeon may also remove nearby lymph nodes in the neck. These can be tested for signs of cancer.
Radioactive iodine: This treatment uses large doses of radioactive iodine, after doing a thyroidectomy, to destroy any remaining healthy thyroid tissue as well as microscopic areas of thyroid cancer that weren't removed during surgery. It may also be used to treat thyroid cancer that recurs after treatment or that spreads to other areas of the body. Radioactive iodine treatment comes as a capsule or liquid that can be swallowed.
External radiation therapy: External beam radiation therapy may be recommended if surgery isn't an option and the cancer continues to grow even after radioactive iodine treatment. Radiation therapy may also be recommended after surgery if there is an increased risk that the cancer will recur.
Chemotherapy: Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. Chemotherapy is not commonly used in the treatment of thyroid cancer, but it's sometimes recommended for people with some sub-types of thyroid cancer. Chemotherapy may be combined with radiation therapy.
Targeted drug therapy: Targeted drug treatments focus on specific abnormalities present within the cancer cells. By blocking these abnormalities, targeted drug treatments can cause the cancer cells to die. Targeted drug therapy for thyroid cancer targets the signals that tell the cancer cells to grow and divide. It's typically used in advanced thyroid cancer.
- Higher serum TSH in thyroid cancer patients occurs independent of age and correlates with extrathyroidal extension. Megan R. Haymart, Simone L. Glinberg, et.al. Clin Endocrinol (Oxf). 2009; 71(3): 434–439
- Diagnosis and Treatment of Patients with Thyroid Cancer. Quang T. Nguyen, et.al. Am Health Drug Benefits. 2015;8(1):30-40