Papillary thyroid cancer is the most common type of thyroid cancer, making up approximately 80% of all thyroid cancers. Most patients present with a nodule (lump) in their neck or after having an ultrasound or other imaging study that shows a thyroid nodule. Papillary cancer tends to grow slowly and may spread to the lymph nodes in the neck, but still usually has an excellent prognosis. Most patients with papillary thyroid cancer can be successfully treated with a thorough initial operation, and some patients may require additional treatment with radioactive iodine.
Follicular thyroid cancer is the second most common type of thyroid cancer, making up 10-15% of all thyroid cancers. It may spread to the lymph nodes in the neck, and is also more likely than papillary thyroid cancer to spread through the blood stream to distant areas (such as the lungs). The prognosis for follicular thyroid cancer remains very good.
Hurthle cell cancer is a rare type of follicular thyroid cancer that has many pink-staining cells (so-called oncocytes or Hurthle cells). The pathologist will look for signs of cancer cells invading into surrounding blood vessels or breaking outside of the thyroid, which may predict that the cancer will behave more aggressively.
Medullary thyroid cancer makes up 5-10% of all thyroid cancer cases. It is often associated with hereditary conditions (MEN-2), and all patients should undergo genetic testing for a RET gene mutation. If a mutation is found, then the patient’s family members may be at risk for medullary thyroid cancer.
Poorly differentiated and anaplastic (also known as undifferentiated) thyroid cancer means that the cancer cells do not look or behave like normal thyroid cells. Patients usually present with a rapidly growing neck mass. These are very rare types of thyroid cancer, and occur in less than 2% of cases. Unfortunately they tend to be very aggressive and not responsive to treatment.