Papillary vs. medullary thyroid cancer

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Papillary and medullary thyroid cancers affect the thyroid gland, but they start in different types of cells.

Papillary thyroid cancer is a type of differentiated thyroid cancer, which means it starts in cells that make and release thyroid hormones. It typically forms in only one lobe of the thyroid gland, and about 80% of people with thyroid cancer have this type. While it grows slowly, it often spreads to lymph nodes in the neck.

Medullary thyroid cancer is less differentiated and forms in C cells, which produce calcitonin. Calcitonin is a hormone that helps regulate calcium levels in the blood.

Sometimes, medullary thyroid cancer can spread to the lymph nodes, the liver, or lungs even before the discovery of a thyroid nodule or lump. It is much less common than papillary thyroid cancer, accounting for only 4% of people with thyroid cancer.

Medullary is more aggressive than papillary thyroid cancer. Doctors categorize the latter as a nonaggressive type of cancer.

Papillary cancer is rarely fatal, even if it has spread to nearby lymph nodes. Treatment usually works to stop the spread and cause remission.

However, some less common subtypes can grow faster. In the early stages, these types of papillary thyroid cancer have the same favorable outlook as the most common subtype, but if they are more advanced, this may affect the prognosis.

Medullary cancer is more difficult to detect and treat than papillary thyroid cancer. However, the prognosis does not differ significantly from the papillary type until the later stages, after the cancer has spread to distant body parts.

The outlook depends on the stage of the thyroid cancer at diagnosis. It may be:

• localized, meaning the cancer does not extend beyond the thyroid gland
• regional, meaning the cancer has spread to structures near the thyroid gland, such as lymph nodes
• distant, meaning the cancer has spread to distant parts of the body far from the original site

The chart below compares the 5-year relative survival rates of the two types of cancer. This statistic shows how likely it is that people with a specific type and stage of cancer will live at least 5 years after their diagnosis compared to the general population.

The exact cause of most thyroid cancers is unknown. Changes in a person’s DNA can cause cells to become cancerous, but it is not always clear why this happens to some people and not others.

Sometimes, people inherit genetic differences that predispose them to cancer. This can occur in papillary and medullary thyroid cancer, but it is more common in medullary thyroid cancer.

Statistics indicate that around 5% of people with papillary and follicular thyroid cancer develop it because others in the family have had the same condition. For medullary, there is familial occurrence in 15–30% of people.

Other risk factors for thyroid cancer include:

• a diet too low or high in iodine
• radiation exposure, particularly in childhood
• having obesity

For localized or regional papillary thyroid cancer, treatment may involve:

• total thyroidectomy, which is the removal of the entire thyroid gland, or a lobectomy, which is the surgical removal of one lobe of the thyroid gland
• radioactive iodine therapy (RAI), which helps destroy remaining thyroid gland tissue after surgery
• thyroid suppression therapy, which is a treatment that helps prevent further growth of thyroid tissue
• external-beam radiation therapy (EBRT)

If the cancer has spread to other parts of the body and it responds to RAI, treatment may include RAI and suppression therapy. If it does not, doctors may recommend the following:

• surgery
• thyroid suppression therapy
• chemotherapy
• targeted therapy
• EBRT

For localized medullary thyroid cancer, treatment typically involves surgery to remove the thyroid and EBRT. If it has spread further afield, treatment may involve targeted therapy. If the cancer has advanced, a person may require palliative care to relieve symptoms and improve quality of life as much as possible.

Follicular thyroid cancer is another type of differentiated thyroid cancer. Approximately 10% of people with thyroid cancer have follicular thyroid cancer. However, unlike papillary and medullary cancer, it typically does not spread to the lymph nodes.

Follicular thyroid cancer can spread to other parts of the body, such as the bones or lungs. Typically, follicular cancer has a favorable outlook but less favorable than the outlook for papillary cancer. The survival rates are similar to papillary cancer.

Anaplastic thyroid cancer is an undifferentiated type of thyroid cancer, which means the cancer cells do not resemble typical thyroid gland cells. Anaplastic thyroid cancer is rare, accounting for about 2% of people with thyroid cancer.

Unlike papillary thyroid cancer, which spreads slowly, anaplastic thyroid cancer spreads rapidly to the neck and other parts of the body. It is challenging for doctors to treat.

There are several key differences between papillary and medullary thyroid cancer. Papillary is much more common than medullary, and it usually has a favorable outlook when a person receives prompt treatment.

Medullary thyroid cancer has lower survival rates once it becomes advanced. Its prognosis is similar to papillary thyroid cancer in its early stages. However, it can spread to distant body parts before detection, making it harder for doctors to treat.

Although the causes of most thyroid cancers are unknown, heredity plays a role. Familial occurrence is more common in medullary thyroid cancer than papillary thyroid cancer.