The chance of receiving a diagnosis of thyroid cancer—a cancer of the butterfly-shaped gland in the front of the neck that plays an important role in metabolism—has more than doubled in the last 30 years. This makes thyroid cancer the most rapidly increasing cancer in the United States, according to a January 2016 report from the American Cancer Society.

Why We're Seeing More Thyroid Cancer

But this increase in the diagnosis of thyroid cancer doesn't necessarily mean that rates of the disease are skyrocketing. The surge in this diagnosis appears to be primarily due to an increase in the use of thyroid ultrasound imaging tests, which can detect thyroid nodules that are so small they might otherwise have never been noticed.

If biopsied, such thyroid nodules may show cancer, but are generally considered unlikely to cause harm: “Most (such) cancers don’t need treatment because they grow slowly, or not at all,” says H. Gilbert Welch, M.D., a professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice in Hanover, N.H., and author of "Overdiagnosed: Making People Sick in the Pursuit of Health" (Beacon Press, 2011).

For example, in a study published in 2014 in JAMA Otolaryngology—Head & Neck Surgery, Welch and colleague Louise Davies, M.D., looked at statistics on adults diagnosed with thyroid cancer between 1975 and 2009 in nine areas of the U.S. They found that the increases in diagnoses of thyroid cancer were primarily related to these typically harmless thyroid nodules. 

About Thyroid Cancer Death Rates

It’s also important to know that although thyroid cancer diagnoses have risen, deaths from the disease have not. According to a study published in 2015 in the journal Thyroid—which looked at thyroid cancer cases, deaths, and detection methods in a Minnesota county between 1935 and 2012—the number of deaths from the disease has remained stable since 1970.

Do You Need a Thyroid Ultrasound?

You don’t need a thyroid ultrasound unless you have certain risk factors, such as a family history of thyroid cancer or have been exposed to radiation (during radiation therapy, for example), or if you or your doctor notice a lump in your neck.

If you have a lump or nodule that is small (less than 1 centimeter), talk with your doctor: You can often simply monitor it to ensure that the nodule is not growing, and thus, avoid biopsy and possible surgery, which in rare cases can damage your vocal cords and might require you to take thyroid hormone for the rest of your life.

Your doctor will likely recommend a biopsy to determine whether or not you have thyroid cancer if you have a nodule that's large enough to be felt (typically, bigger than 1 centimeter) or the nodule appears to be rapidly increasing in size. And if cancer is found, you and your doctor will need to discuss treatment options based on the size of the tumor and whether the cancer has spread and where—within the thyroid gland or elsewhere in your body.