Types of Thyroid Cancer

Understanding a thyroid cancer diagnosis can be confusing. There are many different types of thyroid cancer, with varying survival rates and multiple names. 

Whether papillary or follicular thyroid cancer, hereditary or sporadic medullary thyroid cancer, or undifferentiated anaplastic thyroid cancers, these growths start in the thyroid.

The thyroid is a small organ (called a gland) in the front of the throat, near the base of the neck. It is butterfly shaped, with two lobes. It helps the body regulate essential functions, including metabolism, blood pressure, heart rate, and temperature by releasing proteins called hormones that act on other parts of the body. 

Several types of cancer and benign growths can develop in the thyroid—some more dangerous than others. Thyroid cancers are growths of abnormal cells in the thyroid that have the potential to spread and take over other tissues and organs in the body. Thankfully most are successfully treated—more than 900,000 people live with thyroid cancer in the United States.

This article will outline the various types of thyroid cancer and highlight their differences. 

Types of Thyroid Cancer

The thyroid gland contains two types of cells, which perform different functions, as follows:

• Follicular cells make hormones that regulate metabolism, blood pressure, and heart rate.
• C cells (or parafollicular cells) make a hormone that helps the body use calcium.

Immune system cells called lymphocytes and structural cells called stromal cells also populate the thyroid. 

Any of these cells can mutate into cancer cells. Which cells become cancer determines what type of thyroid cancer you have. Different types of thyroid growths and cancers have different symptoms and prognoses.

Several benign (noncancerous) growths can develop in the thyroid. They include a thyroid enlargement called a goiter, which may make the thyroid larger than usual or develop lumps or bumps. Goiters don’t spread to other body parts and are not usually life-threatening. 

Another benign condition is thyroid nodules, which appear as lumps in the thyroid. In about 5%–15% of cases, thyroid nodules can develop into cancer, but most do not.

Some growths in the thyroid are malignant (cancerous), which means they can grow into other tissues and spread to other parts of the body.

Thyroid malignancies include three types of differentiated thyroid cancers (papillary, follicular, and Hürthle cell cancers), medullary thyroid cancers (MTC), and undifferentiated cancers, including anaplastic thyroid cancers. 

"Differentiated" means these cells in these cancers still look similar to the normal thyroid cells from which they develop. Undifferentiated cancers look less normal under the microscope. Their genetics have changed to the point where they grow faster and have an easier time spreading to the rest of the body.

Differentiated

The three types of differentiated thyroid cancers (DTC)—papillary, follicular, and Hürthle cell—make up the majority of thyroid cancers. They all develop from the follicular cells that make up most of the thyroid gland. 

Papillary Thyroid Cancer

Papillary thyroid cancer is differentiated thyroid cancer. About 80% of thyroid cancers are papillary cancers. They’re also known as papillary carcinomas or papillary adenocarcinomas. They are typically slow-growing and confined to one lobe of the thyroid. 

Treatment of papillary thyroid cancer, even when it has already spread to the lymph nodes, usually is successful. These cancers are rarely fatal.

Follicular Thyroid Cancer

The second most common type of thyroid cancer is follicular thyroid cancer, also known as follicular carcinoma or follicular adenocarcinoma. It accounts for a little over 10% of all thyroid cancers. The most common cause is a lack of iodine in the diet, so it’s more common in areas where people don’t get enough of this essential nutrient. 

Follicular thyroid cancer has a slightly worse outlook than papillary thyroid cancers and more commonly spreads to the lungs or bones, bypassing the lymph nodes. Especially when caught early, follicular thyroid cancer has a very good prognosis.

Hürthle Cell Thyroid Cancer

Also called oxyphil cell carcinoma, Hürthle cell cancers are rare. They make up about 3% of thyroid cancers. This cancer is harder to discover and treat and, therefore, has a worse prognosis. 

Medullary Thyroid Cancer (MTC)

Medullary thyroid cancer (MTC) is also differentiated cancer, but it develops from the thyroid’s C cells. It is rare, accounting for 2%–4% of thyroid cancers. It is more aggressive than the thyroid cancers described previously.

MTC is often discovered in the lymph nodes, lungs, or liver before a healthcare provider finds a thyroid lump. These rare cancers are more difficult to find and treat.

Sporadic MTC

About 80% of MTC cases are sporadic, meaning they arise without previous inheritance of a genetic mutation. These cases of MTC tend to be confined to just one lobe of the thyroid and typically pop up in older adults.

Familial MTC

Some cases of MTC, about 20%–25%, happen because of a genetic mutation and can be passed down in families. Because a specific genetic mistake in the gene RET causes these cancers, they arise earlier—in childhood or early adulthood. Familial MTC can occur as part of multiple endocrine neoplasia type 2 (MEN-2) disorders. 

In familial MTC, cancerous cells are widespread throughout both thyroid lobes and spread quickly to other parts of the body.

Anaplastic Thyroid Cancer

Anaplastic thyroid cancer is also called undifferentiated thyroid carcinoma. Undifferentiated means the cancer cells look wild in the microscope—they've changed a lot from the normal cells of the thyroid that they originated from.

Sometimes, these cells are the same cells that give rise to differentiated thyroid cancers, but cancer has changed them so much that they’re unrecognizable.  

Anaplastic thyroid cancer has the worst prognosis of any thyroid cancer, but, luckily, it’s also the rarest. Only 2% of thyroid cancers are undifferentiated. These cancers spread quickly to tissues in the neck and other body parts, making them very hard to treat.

Less Common Types of Thyroid Cancers

Thyroid cancers can also develop from other cells present in the thyroid, including lymphomas from lymphocytes and sarcomas from stromal cells. These rare tumors make up less than 4% of thyroid cancers.

Parathyroid Cancers

A gland closely related to the thyroid, called the parathyroid, can also give rise to cancerous tumors. Parathyroid cancers are not the same as thyroid cancers. Parathyroid cancers are very rare—fewer than 100 are found each year in the United States.

The four small parathyroid glands are located behind the thyroid. They work to regulate the body’s calcium levels and can cause a variety of symptoms due to high calcium levels. These cancers are harder to cure than thyroid cancers.

Summary

Thyroid cancers are growths that develop on the thyroid that can spread to other tissues and parts of the body. There are several types, including differentiated thyroid cancers (papillary, follicular, and Hürthle cell cancers), sporadic and hereditary medullary thyroid cancers, and undifferentiated (anaplastic) thyroid cancers. 

The vast majority of thyroid cancers are easily treatable and have a very good survival rate. 

A Word From Verywell

A large percentage of thyroid cancers are treatable and even curable. Healthcare providers often catch these cancers early, and most patients are alive five years after diagnosis. If you’ve been diagnosed with thyroid cancer, treatment should allow you to live a long and healthy life.