What is Thyroid Cancer?
The thyroid gland is located in the front of the neck, just below the Adam’s apple. The gland is shaped like a butterfly and wraps around the windpipe. The two wings or lobes on either side of the windpipe are joined together by a bridge, called the isthmus, which crosses over the front of the windpipe.
Thyroid cancer occurs in all age groups, although its rate increases with age, especially after 30 years of age. The more aggressive forms of thyroid cancer are found in older patients.
READ ALSO: Thyroid Disorders: Symptoms and Solutions
Thyroid cancer occurs three times more frequently in women than in men. Thyroid cancer originates from one of two different types of thyroid cells: follicular cells (parafollicular), or C cells.
Symptoms of Thyroid Cancer
Thyroid cancer is associated with a lump that sometimes can be felt in the front of the throat. Most thyroid nodules are non-cancerous only very few are cancerous.
Rarely, thyroid cancer can present with other symptoms such as neck enlargement, difficulty breathing or swallowing, hoarseness, swollen lymph nodes, weight loss, cough, and neck pain
Thyroid Cancer Causes
There are four major types of thyroid cancers, listed below in order of decreasing frequency:
Papillary (includes follicular variant papillary thyroid carcinoma)
Papillary thyroid cancer (PTC) is the most common type of thyroid cancer and accounts for more than two-thirds of all thyroid cancers. People who have had neck or head radiation therapy are at a higher risk of developing this cancer.
READ ALSO: Natural Ways to Get Rid of Gallstones
Most patients will not die from papillary thyroid cancer. They are considered low risk if:
- There is no invasion of surrounding structures and they are younger than 45 years of age.
- They have small tumors.
- No distant spread or metastasis.
Follicular variant papillary thyroid cancer is a type of papillary thyroid cancer that has a survival rate similar to that of papillary thyroid cancer. Overall, papillary thyroid cancer is associated with a high survival rate.
Follicular (includes Hurthle cell and insular carcinoma)
Follicular thyroid cancer (FTC) develops from the follicular cells and tends to grow slowly. This cancer occurs more in older patients compared to papillary thyroid cancer. The diagnosis of “malignancy” depends on the spread to local tissue and blood vessels. Like papillary thyroid cancer, the patient’s age, size of tumor, and the extent that the tumor has spread can envisage severity of disease.
Medullary carcinoma of the thyroid originates from the thyroid parafollicular, or C cells. C cells produce a hormone called calcitonin, which can be measured and used as a marker of medullary carcinoma. Medullary carcinoma can occur intermittently with no association, with other endocrine diseases, or may have a genetic basis when associated with familial medullary carcinoma or the multiple endocrine neoplasia syndromes (MEN). Multiple endocrine neoplasia syndromes are a group of endocrine diseases that result from an inherited gene mutation. With multiple endocrine neoplasia syndromes which include medullary carcinoma of the thyroid, the adrenal glands, the parathyroid glands, and the surface of the mouth may be affected in addition to the thyroid.
The manner of presentation is different when comparing the sporadic form usually presents with a solitary thyroid mass, whereas the hereditary form usually presents with bilateral thyroid masses in a multifocal fashion.
Medullary carcinoma can include multiple tumors in both lobes of the thyroid and frequently spreads to local lymph nodes, both in the neck and the mediastinum.
Anaplastic thyroid cancer
Anaplastic thyroid cancer is a rare type of thyroid cancer. Some genetic mutations are related to some thyroid cancers. Damage to DNA can cause these gene mutations due to changes that occur during the natural aging process, radiation exposure, or radiation treatments (as used in the past for skin and head and neck conditions).
Thyroid Cancer Diagnosis
The diagnosis of thyroid cancer is usually by examination of cells gotten from a fine-needle aspiration biopsy or a surgical biopsy of a thyroid nodule.
In a fine-needle aspiration biopsy, a thin needle is introduced through the skin into the thyroid nodule and cells are withdrawn into a syringe and sent to the lab for analysis.
Blood tests are generally not useful in determining whether a particular thyroid nodule is cancerous. Most patients with thyroid cancer have normal blood levels of thyroid hormones, including a thyrotropin (TSH) level.
Thyroid Cancer Treatment
Surgery can be performed to remove all cancer in the neck and any cancerous lymph nodes is the initial therapy for most thyroid cancers. Complications are rare when the method is performed by an experienced thyroid surgeon.
Radioactive Iodine using I-131 is typically used as a follow-up to surgery treatment in papillary and follicular thyroid cancers to destroy any remaining thyroid tissue in the neck. This treatment is usually given two to six weeks following thyroid surgery. It involves giving high doses of I-131 in a liquid or pill form. Patients undergoing this treatment must restrict their dietary consumption of iodine for approximately five to14 days before the treatment and must restrict their contact with children and pregnant women for three to seven days after treatment.
Radiation therapy is used in patients with cancer that cannot be treated with surgery or is insensitive to radioactive iodine, as well as for older patients with cancer that has distant spread. Radiation is sometimes combined with chemotherapy.
Classical chemotherapy is rarely useful, but sometimes tried for progressive diseases that was proved abortive by radioactive iodine or radiation.
There are two new approved targeted agents for the treatment of metastatic medullary thyroid carcinoma. These drugs are vandetenib (Capresa) and cabozantinib (Cometriq). Also, Lenvima (levatinib) has recently received FDA approval for the treatment of refractory differentiated thyroid cancers of papillary and follicular type. Levima appears possibly more effective than sorafenib (Nexavar).
Treatments for the four thyroid cancer types
Papillary thyroid cancer responds to treatment with surgery and radioactive iodine.
Follicular thyroid cancer responds to treatment with surgery and radioactive iodine treatment.
Medullary thyroid cancer must be treated with surgical removal of the entire thyroid gland in addition to complete removal of all neck lymph nodes and fatty tissue. This type of cancer does not respond to radioactive iodine therapy and has a much lower cure rate than either papillary or follicular thyroid cancer. After surgery, patients should be followed every six to 12 months with blood calcitonin and CEA levels to watch for recurrence.
Anaplastic thyroid cancer often cannot be cured with surgery by the time of diagnosis (due to spread of the disease). This cancer is not responsive to radioactive iodine and may require radiation and chemotherapy, or even tracheotomy if the disease is locally advanced and is causing impingement on an airway.