Hurthle cell thyroid cancer is usually classified as a type of follicular thyroid cancer, although it is really a distinct kind of tumor because it grows more aggressively, making up only about 3% to 5% of all types of thyroid cancer, according to the American Cancer Society.
This article walks you through Hurthle cell thyroid cancer basics, including who is most at risk, how it is diagnosed, and and the common treatments recommended for Hurthle cell carcinoma. Hurthle cell cancer is also called Hurthle cell thyroid carcinoma.
A Hurthle cell is thyroid tissue that has a distinct look under the microscope; it is bigger than a follicular cell and has pink-staining cellular material. Sometimes pathologists classify these cells as enlarged pink-staining oncocytic cells.
How is a Hurthle Cell Tumor Evaluated?
Like follicular tumors, there are both benign and malignant (cancerous) Hurthle cell tumors, and the pathologist evaluates the cells to look for differences that show an invasion of the capsule and the blood vessels. Benign Hurthle cell tumors are harmless and typically do not come back once they are removed.
Hurthle cells look different than other types of thyroid cells, and they tend to occur most often in older patients. The median age of patients with Hurthle cell cancer is 55 years old, about 10 years older than patients with follicular cancer.
Although follicular cancer rarely spreads to lymph nodes, Hurthle cell thyroid cancer is more often diagnosed after invading the lymph nodes in the neck in about 25% of patients. In addition, Hurthle cell thyroid cancer may spread to the lung or bone.
Because younger patients with thyroid cancer tend to have a better prognosis than older patients with a very similar tumor, and because Hurthle cell cancers occur in older patients, they have the reputation of being more dangerous. However, when the research has been controlled for age and other factors like size and initial extent of tumor (whether it has spread locally in the neck or to other parts of the body), Hurthle cell tumors can behave very similarly to follicular tumors.
A small Hurthle cell cancer that does not have extensive growth beyond the thyroid gland, especially in a younger patient (under 55 years old), can have an excellent prognosis.
Most patients who have Hurthle cell cancer will not know they have it until after undergoing thyroid surgery. However, for someone who receives this diagnosis, there are a few facts about Hurthle cell thyroid cancer that may help in seeking the right care:
If you have had a fine needle aspiration biopsy of a lump in your thyroid gland or neck, and your doctor tells you that it is a Hurthle cell tumor or is showing Hurthle cell changes, be sure this is confirmed by a surgeon with expertise in this type of cancer. This is important because most thyroid surgeons seldom see this type of cancer and so do not have the specialized skills to assure the best surgical outcome.
It is important to know that early disease in Hurthle cell thyroid cancer usually has no symptoms. Also, Hurthle cell thyroid cancer hardly ever causes hyperthyroidism (increased thyroid hormone production) or hypothyroidism (low thyroid hormone production).
Detection of Hurthle cell thyroid cancer may first be noticed by a patient who frees or family member who sees a lump in the neck or throat, or by a doctor who detects a lump or nodule when examining a patient's thyroid gland.
Sometimes, suspicious cells are noticed on x-ray studies that were taken for an unrelated medical evaluation. Also, Hurthle cell cancer produces many proteins. While the main protein, thyroglobulin, is produced by a healthy thyroid gland, Hurthle cell cancer will cause a much higher level of this protein to be produced and sheds other molecules that may be picked up as abnormalities in blood tests.
When Hurthle cell thyroid cancer grows outside the thyroid gland, and into the neck, it can produce changes in vocal quality (voice) and may create a noticeable sensation when swallowing. If these symptoms arise, they are urgent signs to seek help from a specialist in thyroid cancer.
Once a small lump is noticed or felt, the likely next step is for your doctor to order a biopsy of the thyroid mass to confirm the presence of Hurthle cells; however, a biopsy cannot distinguish between benign, Hurthle cell changes, or cancerous cells.
Therefore, the likely next step is for your doctor to order an ultrasound, which is much more sensitive than even the most experienced hands. An ultrasound analysis is essential to assess the extent of Hurthle cell tumor growth, including a close examination of the throat and sides of the neck. Often a biopsy is performed at this time to take a tissue sample for later review.
If there is any apparent abnormality involving the lymph nodes of the neck, the doctor may order a CT scan with contrast to gain a clearer picture.
The radiologist (who reviewing imaging results) and the pathologist (who assessing the tissue) are looking for an invasion of the Hurthle cell into the thyroid capsule that distinguishes this form of thyroid cancer. Also, an assessment will be made to determine whether or there is any growth of Hurthle cells into the blood vessels or lymph vessels, any of which is required for a diagnosis of Hurthle cell cancer. The lymph nodes will also be assessed for signs of tumor growth.
When abnormal changes of the thyroid and/or neck lymph nodes are detected, a biopsy may be ordered. When there is any suspicion of Hurthle cell invasion into adjacent tissue, the surgeon will likely order a CT scan with contrast for a closer assessment of the neck.
If the cells are determined to have Hurthle cell changes, this usually means a favorable diagnosis of follicular thyroid cancer that is cured by removal of thyroid (thyroidectomy).
What If You Have Thyroiditis?
Some people will have an inflammatory condition affecting their thyroid, called thyroiditis. The most common cause of thyroiditis is Hashimoto's thyroiditis, which is an autoimmune reaction that leads to hypothyroidism. Thyroiditis also may occur in individuals receiving treatment with interferon or amiodarone.
In individuals who have thyroiditis and receive a diagnosis of Hurthle cell thyroid cancer, the thyroglobulin level is likely to appear as zero because the antibodies are clumped with the thyroglobulin protein, making them undetectable in a blood test. Therefore, relying on blood tests is not ideal when trying to make an accurate diagnosis of Hurthle cell thyroid cancer.
Surgery: For most individuals, the best and the often the only course of treatment is surgical removal of the entire thyroid gland and associated lymph nodes. This can usually be accomplished as a minimally invasive procedure with just a small incision on the lower part of the neck.
Patients with Hurthle cell thyroid cancer will usually be advised to undergo removal of all or nearly all their thyroid tissue, particularly when there is significant evidence of a tumor, based on size and activity, in the thyroid gland, possibly involving lymph nodes. (See our article on the different types of thyroid surgery).
In all areas of well-differentiated thyroid cancer, there is some disagreement about how extensive the surgery should be; however, because Hurthle cell tumors tend to occur in patients with more serious risk factors, the surgery is correspondingly more aggressive. If there are involved lymph nodes, they are removed, although this is uncommon.
Surgery may be followed with radioactive iodine. Radioactive iodine does not work as well for Hurthle cell cancer as it does for follicular cancer because the Hurthle cells are less likely to "take up" the radioactive iodine and then be destroyed by it. However, it is a well-tolerated treatment and may be helpful in some cases.
Radioactive Iodine Treatment (RAI) may be recommended for select patients following a total thyroidectomy when there is evidence of invasion of the Hurthle cell cancer (metastasis) beyond the thyroid gland, and appears highly aggressive.
Sticking to regular follow-up visits is very important for two reasons:
Patients are monitored at six-months and then yearly intervals to make certain that you remain healthy, especially for patients over age 55 years old. Follow--up visits are likely to include a physical examination of the neck, an ultrasound of the neck, and blood tests to check thyroid hormone levels.
The frequency of your follow-up visits may vary depending upon your age at the time of diagnosis, the location, size, and extent of the tumor and any noted spread of the Hurthle cancer cells beyond the thyroid gland.
It's important to treat Hurthle cell carcinoma early. Fortunately, there are several treatment options for Hurthle cell thyroid cancer. Your doctor will walk through all of your treatment options with you.
Getting a high-resolution ultrasound that is assessed by a surgeon specializing in Hurthle cell thyroid cancer is the best way to assure that you will avoid the risk of persistent or recurrent cancer.
A special thank you to James Norman, MD, in recognition of his contributions to the original content on this page.