Thyroid cancer is a disease in which cells in the thyroid gland grow uncontrollably and develop into cancer. Of the 44,000 or so Americans diagnosed with thyroid cancer each year, 98% will survive for 5 years or longer. Treatments are effective against most types of the disease.
Thyroid cancer is three times more common among women than men, and it often occurs in people in their 40s and 50s. People of European heritage are most often affected.
“For the minority of thyroid cancer patients whose disease is not controlled by surgery and radioiodine, new treatments have been approved over the past 10 years that improve survival,” says Hari Deshpande, MD, an associate professor of medicine (medical oncology) at Yale Medicine.
What is thyroid cancer?
Thyroid cancer occurs when cells within the thyroid mutate and grow uncontrollably, leading to the formation of tumors. The thyroid is a small, butterfly-shaped gland in the neck that produces hormones that help to regulate the body’s metabolism.
When a person develops thyroid cancer, it may affect their thyroid function, leading to the production of more or less thyroid hormone than usual. However, some people don’t notice any changes in their bodies, especially if they have a slow-growing or early-stage thyroid cancer.
There are several common types of thyroid cancer:
- Differentiated thyroid cancers. The majority of thyroid cancers are differentiated.When examined under a microscope, the cells that make up differentiated tumors look similar to normal cells. They typically grow and spread more slowly than undifferentiated tumors. There are three types of differentiated thyroid cancer: papillary, follicular, and Hürthle cell.
- Medullary thyroid cancer (MTC). This type of cancer develops from the C cells in the thyroid gland. MTC makes up around 4% of all cases of thyroid cancer.
- Anaplastic thyroid cancer. Also known as undifferentiated thyroid cancer, the cells that make up this type of cancer look abnormal when examined under a microscope. Anaplastic thyroid cancers grow and spread quickly and are difficult to treat.
About 80% of all thyroid cancers are papillary, which is a slow-growing, non-aggressive form of cancer with a high survival rate. The most aggressive type of thyroid cancer is anaplastic; this rare—and serious—form of cancer accounts for about 2% of people with thyroid cancer.
What causes thyroid cancer?
Experts aren’t sure of the exact cause of thyroid cancer. Sometimes, thyroid cells mutate over time because an individual was exposed to radiation during childhood or during previous cancer treatment. Other times, genetic mutations run in the family, causing cells within the thyroid to mutate and multiply. For many, the reason is unknown.
What are the symptoms of thyroid cancer?
Thyroid cancer doesn’t always cause noticeable symptoms. Often, doctors find a nodule or lump when they physically examine a person’s neck or when they order a head-and-neck imaging test for another reason.
Sometimes, an individual visits the doctor because they’ve discovered a suspicious, painless lump or mass in the neck. However, not all lumps are signs of thyroid cancer. In fact, only 10 to 15% of thyroid nodules are found be cancerous; most are benign.
Other signs—aside from thyroid nodules—that may suggest thyroid cancer include:
- Swollen lymph nodes in the neck
- Difficulty speaking
- Trouble swallowing
- A high-pitched sound that happens while inhaling
- A choking feeling
- Pain that develops within a lump or mass in the neck
- Facial flushing or redness
What are the risk factors for thyroid cancer?
The highest risk for thyroid cancer is among females who are white and middle-aged. Factors that increase risk include:
- Exposure to radiation during childhood (especially to the head and neck)
- Having a family history of thyroid cancer
- Insufficient dietary iodine
Additionally, people may be at increased risk of thyroid cancer if they have any of the following medical conditions:
- An enlarged thyroid or goiter
- Benign thyroid nodules or lumps
- A previous thyroid cancer diagnosis
- Graves’ disease
- An inherited condition which may cause multiple benign thyroid tumors, such as Carney complex type 1, Cowden disease, or Gardner syndrome
How is thyroid cancer diagnosed?
A combination of criteria is used to diagnose a patient with thyroid cancer.
Learning about the patient’s personal and family medical history can provide key information. A doctor will want to know if the patient was exposed to radiation during childhood, if the person has had other thyroid abnormalities over time, and if others in the family have had thyroid cancer.
If the patient has a noticeable lump or nodule in the neck, the doctor will physically examine it. However, it’s not possible for doctors to tell whether or not a thyroid lump or mass is cancerous through touch. If the doctor suspects thyroid cancer, they will order tests to confirm.
Often, doctors order an ultrasound, which is the preferred imaging test to identify thyroid cancer. Ultrasounds can detect thyroid nodules and lymph node abnormalities that suggest the cancer has spread. Other imaging tests, including CT scan and MRI, are sometimes, but less commonly, used.
When an ultrasound shows the presence of a solid mass or nodule within the thyroid, doctors biopsy the tissue to determine whether it’s cancerous. They typically perform a fine-needle biopsy.
However, if the test results suggest anaplastic thyroid cancer, the doctor may offer a core biopsy or surgical biopsy after the initial fine-needle biopsy to confirm the cancer type with a larger tissue sample. Regardless of the type of biopsy performed, after a tissue sample is collected, a pathologist analyzes it under a microscope to check for the presence of cancer cells.
It’s important to note that although thyroid cancer can’t be diagnosed with a blood test, some doctors order bloodwork for patients to see if their thyroids are working properly.
How is thyroid cancer treated?
Treatment options vary, depending on the size of the tumor and the type of thyroid cancer.
Treatment may include:
- A watch-and-wait approach. When an individual is diagnosed with papillary thyroid cancer and the tumor is very small (less than 1 cm), a doctor and patient may decide to monitor this slow-growing type of cancer, rather than opting for surgery right away.
- Surgery. Most people with thyroid cancer have part or all of their thyroid surgically removed, along with neighboring lymph nodes. For some types of thyroid cancer, such as early-stage papillary or medullary cancers, removing the thyroid itself may cure the cancer. In other cases, further treatment is needed.
- Thyroid hormone therapy. Once a person has their thyroid completely removed, the body can’t produce thyroid hormone anymore. Because thyroid hormone is necessary to help regulate metabolism levels, doctors usually prescribe synthetic thyroid hormone, which most people will need to take for the rest of their lives.
- Radioactive iodine or “radioiodine” therapy. This treatment is typically given after surgery, to find and destroy any remaining thyroid cells. Because the thyroid absorbs iodine in the body, when radioactive iodine is introduced, it will find its way to any remaining thyroid cells. The radiation helps to destroy those cells.
- External beam radiation therapy. Radioactive iodine therapy isn’t effective against medullary or anaplastic thyroid cancer, but external beam radiation therapy is another type of radiation that helps to destroy cancer cells in these instances. It is often used when cancer cells have spread outside of the thyroid.
- Chemotherapy. This traditional cancer treatment isn’t effective against most types of thyroid cancer, but it may be helpful for anaplastic thyroid cancer or certain types of advanced thyroid cancer. People who need chemotherapy for thyroid cancer may be treated simultaneously with external beam radiation therapy. The combination may help to destroy cancer cells.
- Targeted therapy. Certain newer targeted medications called kinase inhibitors may be used to treat papillary or follicular thyroid cancers that are unresponsive to radioiodine treatment as well as metastatic medullary thyroid cancers and some anaplastic thyroid cancers. These medications usually target abnormal proteins that are caused by mutations in specific genes (e.g. BRAF, RET, and NTRK genes). Because targeted therapy drugs home in on cancer cells, they tend to cause fewer side effects than chemotherapy drugs, which sometimes damage healthy cells while harming cancer cells.
- Ethanol or radiofrequency ablation. Sometimes—when thyroid cancer recurs, for example—doctors may recommend a minimally invasive treatment such as ethanol ablation or radiofrequency ablation to destroy cancer cells. A needle is inserted into the neck, using ultrasound guidance to pinpoint the area where thyroid cells are present. Then ethanol is injected—or heat (radiofrequency)—is applied through the needle. Both of these approaches damage the cancer cells.
What is the outlook for people with thyroid cancer?
A patient’s prognosis varies, depending on the type of thyroid cancer they have and how early it is detected and treated.
Most people with thyroid cancer fully recover. The majority of people with thyroid cancer are diagnosed with papillary cancer, a form that responds very well to treatment. (93% of people survive 10 years or longer.)
Follicular thyroid cancer also responds quite well to treatment; 85% of people survive for 10 years. Hürthle cell and medullary thyroid cancers don’t respond as well as papillary and follicular thyroid cancers, but nonetheless, about 75% of people with these less common forms of cancer survive for 10 years.
Anaplastic thyroid cancer doesn’t respond as well to treatment. Only 14% of people survive 10 years. Early diagnosis and treatment are key.
What makes Yale Medicine unique in its treatment of thyroid cancer?
“Patients who are treated at Yale for thyroid cancer have their case presented at a multidisciplinary tumor board meeting, “says Dr. Deshpande. “Physicians, including radiologists, pathologists, endocrinologists, medical oncologists and surgeons, will review scans and biopsies while listening to a summary of the patient’s medical history. A treatment plan will be made that may include one, more than one, or sometimes all the above specialties. This is especially important when deciding whether to use treatments with potential toxicities and weighing risks and benefits of each option.”
Practice nurses and nurse coordinators help communicate the sometimes confusing and complicated testing and appointment schedules as well as explain how to cope with adverse events that may be experienced after different treatments.
“A diagnosis of cancer is one of the most traumatic events anyone can experience. Having a team of medical professionals to help guide patients through their journey is essential to providing the best and safest care,” says Dr. Deshpande.