Thyroid Cancer

All About the Different Types

The thyroid is butterfly-shaped organ that that produces hormones vital to the normal function of the body by controlling your metabolism, as well as other growth and maturation of the body. It is located just below your larynx (voice box) and surrounds your windpipe. It is reddish-brown in color due to the high number of blood vessels that are present in the thyroid tissue. The thyroid is made up of two main types of cells: follicular and C (parafollicular) cells.

Less common cell types include: lymphocytes (related to the immune system) and stromal (structural support) cells

When the cells within the thyroid create an extra group of cells, a benign tumor can form. Benign tumors do not invade (metastasis) into neighboring tissues or organs. When the cells within the thyroid become altered, divide, and grow, thyroid cancer occurs. Thyroid cancer can metastasize into other parts of the body.

If you notice a lump in the lower portion of your neck (where the thyroid resides), or have other symptoms of thyroid cancer, you should always seek medical attention. Even benign tumors can cause problems for your health if the size impacts other structures of the body, like your airway. In most cases benign tumors of the thyroid do not cause problems and are just monitored.

Different Types of Thyroid Cancer

There are several types of thyroid cancer, that are associated with various affected cells or parts of the thyroid.

Many of the types of cancer originate in the follicular cells, which are responsible for the production of the hormones: T3 (Triiodothyronine) and T4 (Tetraiodothyronine or thyroxine). These two hormones mainly consist of iodine and are considered the proper hormones of the thyroid. The most common type of thyroid cancer is papillary.

Papillary thyroid cancer accounts for about 86% of all thyroid cancer. Papillary cancer starts in the follicular cells (responsible for producing hormones) of the thyroid. It is usually a slow growing cancer and can be cured if identified in early stages

Follicular thyroid cancer originates in the follicular cells of the thyroid. Follicular thyroid cancer is the second most common thyroid cancer, however is much less common than papillary thyroid cancer. Follicular thyroid cancer is the related cause only about 9% of the time. Also similar to papillary cancer, follicular cancer begins in the follicular cells of the thyroid, grows slow, and can usually be successfully treated.

Medullary thyroid cancer originates in the C cells of the thyroid. As such, usually production of high levels of calcitonin is usually noticed. Medullary thyroid cancer is also slow growing and is rare, only being found in about 2% of the cases of thyroid cancer. This type of cancer is more easily controlled if it is caught early before metastasis occurs.

Unique to medullary thyroid cancer, is that it can be genetic. Mutations to the RET gene causes a strong likelihood that you will develop medullary thyroid cancer. If you have the RET gene mutation, you may only develop thyroid cancer (familial medullary thyroid cancer) or you may also develop MEN (multiple endocrine neoplasia) syndrome which leads to the development of other cancers related to the endocrine system. An alternative form of medullary thyroid cancer is not genetic in cause and is known as sporadic medullary thyroid cancer. This is generally found in older adults and accounts for about 80% of the cases of medullary thyroid cancer. There is currently not a known cause for this type of cancer.

If you are found to have the mutated RET gene, your physician may recommend frequent lab tests (usually calcitonin levels). Alternatively, your physician may recommend completely removing your thyroid before cancer develops due to the strong likelihood that medullary thyroid cancer will develop.

Anaplastic thyroid cancer is the least common type of thyroid cancer occurring in only about 1% of the diagnosed cases. Similar to follicular and papillary thyroid cancers, anaplastic thyroid cancer starts in the follicular cells of the thyroid. However unlike the other 3 types of thyroid cancer, anaplastic is fast growing and very difficult to control. Also dissimilar to the other types of cancer, anaplastic thyroid cancer does not tend to be found in younger age groups. When found, it is usually found in individuals greater than 60 years of age.

Thyroid lymphoma is a rare form of thyroid cancer. It is a cancer of the lymphocytes (immune cells) found in the thyroid. This accounts for less than 2% of the thyroid cancers diagnosed and accounts for less than 2% of the lymphomas found outside of the bodies lymph nodes. Treatment is different for thyroid lymphoma than the previous 4 thyroid cancers discussed.

Thyroid sarcoma is a very rare form of thyroid cancer. There is very little research on this type of cancer due to the number of cases found. It is a cancer of the stroma cells (structural support) and is very fast growing and difficult to treat.

Determining the Type of Cancer

Initial assessment of thyroid cancer begins during a physical exam in a physician’s office. The doctor will palpate (feel) around your lower neck for any abnormal masses. If there is concern for thyroid cancer from physical findings or other reasons, the physician will have several options to help diagnose and differentiate one type of cancer from the rest.

Blood work can help identify potential for medullary thyroid cancer. Calcitonin levels and Carcinoembryonic Antigen (CEA) testing may be ordered to help identify risk for either form of medullary thyroid cancer. CEA is typically found in fetuses; however it is abnormal to find high levels in adults.

Ultrasound may be used to find nodules (masses) that are too small to be felt. The physician will also look to see if the masses are fluid-filled (not usually cancer) or solid (has potential to be cancer). Ultrasound will also be used when performing a biopsy (with a small thin needle) to collect a specimen that is used to definitely identify if the nodule is cancerous or not.

Thyroid scans can be performed by having you swallow radioactive iodine. During the scan, the follicular cells of the thyroid will absorb the iodine. Non-cancerous nodules called “hot” nodules will take up more iodine and appear brighter on the scan. Nodules that do not absorb as much iodine (“cold” nodules) will not appear as bright and may have potential to be cancerous. This test is not a definitive test for cancer, but may be used to help identify risk for cancer.

Biopsy of the nodule is the only way to be certain if the nodules are cancerous. A pathologist is used to identify the samples taken from the biopsy, which can be done by aspiration (through an ultrasound guided needle), or by surgery. During a surgical biopsy, they will usually either remove one lobe of the thyroid, or remove the whole thyroid. This is usually only done when a needle biopsy has been unsuccessful.


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PubMed Health. (2015). How does the thyroid work? Retrieved on July 31, 2015 from

U.S. National Library of Medicine. (2013). CEA blood test. Retrieved on July 31, 2015 from

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