Thyroid Cancer – Types
Types of Thyroid Cancer
There are 4 main types of thyroid cancer:
- Papillary (80-85% of cases)
- Follicular (7-15% of cases)
- Anaplastic (1-2% of cases)
- Medullary (3-5% of cases)
There are also several rare (2-4% of cases) sub-types called: Columnar, Tall Cell, Insular, Diffuse Sclerosis, and Hürthle Cell carcinoma (also known as Oxyphil Cell Carcinoma). In these types, the cancer cells are poorly differentiated (don’t resemble healthy cells). They tend to grow and spread more quickly.
Other very rare forms include thyroid lymphoma and thyroid sarcoma.
Papillary is a differentiated form of thyroid cancer (DTC), also referred to as well-differentiated (WDTC). This means that cancer cells still resemble healthy cells to some degree. DTCs originate in the follicular cells of the thyroid. Papillary is by far the most common type of thyroid cancer.
If papillary thyroid cancer metastasizes (spreads), it is likely to be found in the lymph nodes in the neck. People with the papillary type tend to have more than one cancerous nodule in the thyroid gland and in the lymph nodes in the neck and/or chest.
Like papillary thyroid cancer, follicular is also a DTC; Although rare, if follicular thyroid cancer spreads, it is more likely to be found in the lungs or bones. Some patients have a mix of papillary-follicular thyroid cancer.
Anaplastic thyroid cancer (ATC) is a very rare form of thyroid cancer. It is believed that anaplastic thyroid nodules are in the body, undetected, for a long time. Because they weren’t treated, they suddenly became aggressive. ATC spreads rapidly and is much harder to treat. Only about 1.5% of thyroid cancer cases are anaplastic.
Unlike DTCs which originate in the follicular cells of the thyroid, medullary thyroid cancer (MTC) originates in the C cells of the thyroid. C cells do not make thyroid hormone, nor do they take up iodine. For this reason, MTC is not treated with radioactive iodine. Certain blood tests are used to detect MRC. About 4% of thyroid cancer is the MTC form.
There are two known types of MTC:
- Sporadic (80% of cases, often in older adults)
- Familial (usually seen in childhood or early adulthood). This type spreads more rapidly. A blood test can test for the gene that causes familial MTC. If thyroid cancer runs in your family, it’s a good idea to ask your doctor about genetic testing.
Because MTC occurs in a different area of the body than DTC, the symptoms can be different:
|General Symptoms of Thyroid Cancer||Symptoms Associated with Medullary Thyroid Cancer|
|Thyroid and/or neck lymph node nodule(s) that can be felt on touch||Thyroid nodule and an unusually enlarged neck lymph node(s)|
|Hoarseness||Diarrhea (not common)|
|Difficulty breathing||Bumps on lips, eyelids or tongue|
|Difficulty swallowing (“lump in the throat”)||High blood pressure|
|Positive RET (MTC gene) testing|
The vast majority of thyroid cancer patients (>80%) have the differentiated form (papillary or follicular), which has an overall 97% cure rate.
But, in rare cases, thyroid cancer is aggressive, and spreads rapidly or recurs (comes back). A very small subgroup of patients may also have a form of that does not respond well to radioactive iodine treatment.
Why certain cancer cells become more aggressive is not fully understood, and research is underway to try to pinpoint the mechanism and identify effective treatments.