Key Statistics

Global Incidence: An estimated 959,281 people were diagnosed with thyroid cancer worldwide in 2024.

U.S. Incidence: An estimated 45,240 people in the U.S. are expected to be diagnosed with thyroid cancer in 2026.

How Does the Tumor Microenvironment Impact Thyroid Cancer?

Cancer doesn’t grow in isolation. Every tumor lives in a complex neighborhood of cells, structures, and signals known as the tumor microenvironment (TME). Thyroid cancer is no exception. Immune cells, including cancer-fighting T cells, are often found in and around thyroid tumors. However, within the TME, cancer can hijack the system and create a space that favors its survival.

From studying other cancers, scientists know that T cells have built-in “brakes,” called immune checkpoints, that keep them from attacking healthy tissue. For some cancers, the TME can send out signals that turn these “brakes” on, preventing T cells from attacking the tumor. Some thyroid cancers, especially anaplastic thyroid cancer (a rare, fast-growing type), display high levels of a “brake” signal called PD-L1. Researchers have developed cancer immunotherapies called checkpoint inhibitors that block this signal and release the “brakes” from T cells, freeing them to fight cancer again. These checkpoint inhibitors were originally developed for other cancers, and researchers are now looking into whether they can be used to treat aggressive thyroid cancers.

Is Immunotherapy Used for Thyroid Cancer?

Immunotherapy is not typically used to treat papillary thyroid cancer because this type of cancer usually responds well to surgery and radioactive iodine. However, researchers are investigating how immunotherapy could be used when this treatment fails and how to use immunotherapy for other rare and aggressive thyroid cancers.

As mentioned, researchers are studying how checkpoint inhibitors could be used to treat thyroid cancer. Some researchers are investigating whether checkpoint inhibitors work better when combined with targeted drugs, which block specific gene changes that can drive a cancer’s growth. This combination is being explored for anaplastic thyroid cancer because many of these tumors carry a change in a gene called BRAF. Studies suggest that adding a checkpoint inhibitor to drugs that target BRAF may help some patients live longer.

In early clinical trials, researchers are also testing chimeric antigen receptor (CAR) T-cell therapy, in which a patient’s own T cells are engineered to find and destroy cancer cells. As immunologists learn more about how thyroid tumors interact with the immune system, these discoveries are bringing new hope to patients with the hardest-to-treat forms of the disease.

Is Hashimoto’s Thyroiditis Related to Thyroid Cancer?

Hashimoto’s thyroiditis is one of the most common autoimmune disorders and was one of the first diseases identified to be autoimmune. It occurs when immune cells mistakenly attack the thyroid, causing it to become underactive (a condition called hypothyroidism).

Researchers do not fully understand the relationship between Hashimoto’s and papillary thyroid cancer. While increased inflammation in the thyroid from Hashimoto’s may increase the risk of developing papillary thyroid cancer, some studies suggest that ongoing immune activity in the thyroid may also slow tumor growth. Having Hashimoto’s does not guarantee a person will develop thyroid cancer, and researchers are still investigating the relationship.