The incidence of thyroid cancer has been on the rise in the United States, with approximately 45,000 cases occurring each year. Yet, thyroid cancer is very curable and has a fatality rate of only 1,690 per year. Women are affected more often than men, and the disease can occur in any age group, from children to the elderly. There are four main types of thyroid cancer: papillary, follicular, medullary and anaplastic.
Papillary Thyroid Cancer
The most common type of thyroid cancer is papillary, which accounts for around 85 percent of all thyroid cancers. Papillary thyroid cancer typically presents as a nodule within the thyroid gland, which is either felt on exam of the neck or noted on medical imaging studies of the neck.
Needle biopsy is very effective at diagnosing papillary thyroid cancer because of the characteristic changes that can be seen under a microscope. This type of cancer has a tendency to spread to the lymph nodes in the neck, which can increase recurrence rates, but has not been shown to decrease survival.
Papillary thyroid cancer is very sensitive to radioiodine therapy, which is often used routinely following surgical removal of the thyroid and in patients with recurrence of cancer found during surveillance testing. Following surgery and radioiodine therapy office visits, lab tests and ultrasound are recommended every six months for the first year and every year thereafter for five years total.
Follicular Cell Thyroid Cancer
Follicular, or Hurthle cell, thyroid cancer is the second most common form of thyroid cancer and accounts for around 15 percent of all thyroid cancer. Cure rates are also excellent for this type of thyroid cancer, with more than 90 percent of patients cured after treatment.
Diagnosis of this type of cancer prior to surgery is often difficult because needle biopsies are often indeterminate. This is because, unlike papillary thyroid cancer, follicular cancer cells often look very similar to normal thyroid cells, and only invasion of cancer cells through the capsule of the nodule can be used to make the diagnosis of follicular thyroid cancer.
Most patients will undergo complete removal of the thyroid gland and any involved lymph nodes. Follicular thyroid cancer is slightly less responsive to radioiodine therapy than papillary cancer; however, most patients will still receive radioiodine following treatment. Patients are also closely monitored for changes in symptoms.
Medullary Thyroid Cancer
Medullary thyroid cancer accounts for only 4 percent of all thyroid cancers. Dissimilarly to papillary or follicular cancer, this type of cancer does not produce thyroid hormone and therefore does not absorb radioactive iodine.
Medullary tumors arise from the parafollicular (C cells) of the thyroid gland. These cells produce a hormone called calcitonin, which helps to regulate calcium metabolism. Patients with medullary thyroid cancer may have a family history of this type of cancer due to a genetic defect called MENII, although this genetic defect occurs in only a minority of patients.
More aggressive than papillary or follicular cancer, medullary tumors require the removal of the thyroid gland as well as lymph nodes in the neck. Following surgery, a physician provides the patient with a physical exam and ultrasound and measures the patient's calcitonin levels—a sign of tumor recurrence.
Anaplastic Thyroid Cancer
Anaplastic thyroid cancer is very rare but is also the most aggressive. Anaplastic thyroid cancer accounts for less than 1 percent of thyroid cancers, and is more often found in elderly patients. Patients often present with a rapidly enlarging thyroid mass, which is hard and fixed to the surrounding structures of the neck.
Unfortunately, this disease progresses very rapidly and often leads to death within six months of the initial diagnosis. Surgical treatment is often for palliative reasons, and the recurrence rates are high. Clinical trials with radiation and chemotherapy are available.
The treatment of thyroid cancer involves a combination of surgery, radioactive iodine and a close surveillance program. Most thyroid cancer will require removal of the entire thyroid gland and any involved lymph nodes within the neck. Please see the section on thyroid surgery for further information.
Following surgery, patients undergo a radioiodine scan to evaluate for cancer that has spread outside of the neck, and will receive radioiodine therapy to destroy any remaining normal thyroid tissue or thyroid cancer cells. After surgery and radioiodine treatments are completed, patients are followed every six months for a year, and annually thereafter with physical exams, lab tests and an ultrasound of the neck to monitor for cancer recurrence.
After five years of surveillance, more than 95 percent of patients are considered cured and need no further treatment. An endocrine tumor program can provide optimum care for thyroid cancer patients with a multidisciplinary approach, and the most advanced technologies and clinician expertise.