Types of Thyroid Cancer

Thyroid cancer is a type of cancer that starts in the thyroid gland, which makes hormones that help regulate your metabolism, heart rate, blood pressure, and body temperature. The thyroid gland is in the front part of the neck, below the thyroid cartilage (Adam’s apple).

The thyroid gland has two main types of cells:

• Follicular cells: These use iodine from the blood to make thyroid hormones, which help regulate a person’s metabolism.
• C cells (also called parafollicular cells): These make calcitonin, a hormone that helps control how the body uses calcium.

Many types of growths and tumors can develop in the thyroid gland. Most of these are benign nodules (noncancerous) but others are malignant (cancerous), which means they can spread into nearby tissues and to other parts of the body.

Types of Thyroid Cancer

Thyroid cancers are classified according to the appearance of the cancerous cells. Cancerous cells that look like healthy cells are called well-differentiated cells. Well-differentiated cells grow at a slower rate than undifferentiated cells.

An estimated 52,890 adults in the U.S. will be diagnosed with thyroid cancer this year. Women are three times more likely to develop thyroid cancer than men and it's the fifth most common cancer diagnosed in women.

Overall, the 5-year survival rate for people with thyroid cancer is 98%. However, survival rates are based on many factors, including the specific type of thyroid cancer and stage of the disease.

Differentiated

Most thyroid cancers are differentiated cancers. The cells in these cancers look a lot like normal thyroid tissue when seen in the lab. These cancers develop from thyroid follicular cells. Often, differentiated thyroid cancers don't have any symptoms. When symptoms do occur, they can include:

• A small lump/mass in the neck
• Difficulty swallowing
• Pain in the neck and/or throat area
• Hoarseness of the voice

Papillary Thyroid Cancer

About 80% of thyroid cancers are papillary cancers. These cancers tend to grow very slowly and usually develop in only one lobe of the thyroid gland.

Even though they grow slowly, papillary cancers often spread to the lymph nodes in the neck. But even when these cancers have spread to the lymph nodes, they can often be treated successfully with surgery and are rarely fatal.

Follicular Thyroid Cancer

Follicular thyroid cancer (FTC) is the second most common type of thyroid cancer. In most cases, FTC is associated with a good prognosis, although it is somewhat more aggressive than papillary cancer. Follicular carcinomas do not usually spread to nearby lymph nodes, but they are more likely than papillary cancers to spread to other organs, like the lungs or the bones.

FTC is often successfully treated by removing the tumor and affected areas.

Hürthle Cell Thyroid Cancer

Hürthle cell cancer (HCC) accounts for only about 3% to 10% of all differentiated thyroid cancers that arise from a certain type of follicular cell. HCC is much more likely to spread to lymph nodes than other follicular thyroid cancers. HCC is characterized by higher rates of recurrence, metastasis, and cancer-related mortality.

Risk Factors 

Scientists have found a few risk factors that make a person more likely to develop thyroid cancer.

• Gender: Thyroid cancers occur about 3 times more often in women than in men.
• Age: Thyroid cancer can occur at any age, but the risk peaks earlier for women (who are most often in their 40s or 50s when diagnosed) than for men (who are usually in their 60s or 70s).
• Inherited conditions: Thyroid cancer occurs more often in some families and is often seen at an earlier age. The papillary type of thyroid cancer most often runs in families.
• Radiation: Radiation exposure is a proven risk factor for thyroid cancer. Sources of such radiation include certain medical treatments and radiation fallout from power plant accidents or nuclear weapons.
• Iodine in the diet: Follicular thyroid cancers are more common in areas of the world where people’s diets are low in iodine. On the other hand, a diet high in iodine may increase the risk of papillary thyroid cancer.

Medullary Thyroid Cancer (MTC)

Medullary thyroid cancer (MTC) is a rare and aggressive subtype of thyroid cancer that begins when the parafollicular C cells of the thyroid begin to grow abnormally. Medullary thyroid cancer makes up approximately 3% of all thyroid cancers and may be hereditary or sporadic.

MTC is usually treated by removing the thyroid. Besides surgery, sometimes other treatments are also required, such as targeted anti-cancer drugs like Caprelsa (candetanib) or Cabometyx (cabozantinib), as well as radiation therapy and in some cases, chemotherapy.

Sporadic MTC

Accounts for about 80% of cases of MTC, this type is not inherited. It occurs mostly in older adults and often affects only one thyroid lobe.

Familial MTC

Familial MTC is inherited and 20% to 25% can occur in each generation of a family. These cancers often develop during childhood or early adulthood and can spread early. Patients usually have cancer in several areas of both lobes.

If the cancer is located only in the thyroid, it is called localized thyroid cancer. About two-thirds of cases are diagnosed at this stage. The 5-year survival rate is almost 100% for localized papillary, follicular, and medullary thyroid cancers.

Anaplastic Thyroid Cancer

Anaplastic thyroid cancer is rare, accounting for about 1% of all thyroid cancers. This type of cancer can cause severe compression of the structures in the neck, interfering with breathing, swallowing, and speaking. It can also metastasize (spread) rapidly throughout the body. Because this type of thyroid cancer grows so quickly, it is more difficult to treat successfully.

For localized anaplastic thyroid cancer, the 5-year survival rate is 31%.

Less Common Types of Thyroid Cancers

Less than 4% of cancers found in the thyroid are thyroid lymphomas, thyroid sarcomas, or other rare tumors.

Parathyroid Cancers

The parathyroid glands are four small glands located near the thyroid gland in the neck or chest. Almost all tumors that develop in the parathyroid gland are benign. A parathyroid tumor, whether it is benign or malignant, can cause significant problems because this type of tumor causes the amount of calcium in the blood to rise, resulting in a serious condition called hypercalcemia.

Parathyroid cancer is quite rare. There are likely fewer than 100 cases diagnosed each year in the U.S.

A Word From Verywell

For many people with thyroid cancer, treatment may remove or destroy the cancer. It's important to note that care for people diagnosed with thyroid cancer does not end when active treatment has finished. Your healthcare team will continue to check that the cancer has not returned, manage any side effects, and monitor your overall health.