Papillary carcinomas are generally slow growing, with an 80 percent overall survival at 10 years. Even when tumors spread to regional lymph nodes or the lungs, survival may be more than 10 years. Tiny, clinically insignificant papillary carcinomas are found in 5 to 10 percent of thyroid glands examined at routine autopsies.
Follicular carcinomas occur in patients about 10 years older than those who get papillary carcinomas. Although these tumors are also usually slow growing, they behave somewhat more aggressively than papillary carcinomas and are more likely to spread to the lungs or bones. Hurthle cell cancers are generally included with follicular cancers, but are more likely to be multi-focal and involve regional lymph nodes. In contrast to follicular cancers, Hurthle cell tumors also do not take up radioactive iodine.
Three percent of thyroid cancers are undifferentiated (anaplastic) carcinomas. They occur in older patients, grow rapidly, behave aggressively and respond poorly to treatment.
Medullary carcinomas make up about 5 percent of thyroid cancers. These tumors secrete calcitonin, a tumor marker that is helpful in diagnosis and follow-up and also in screening relatives of those affected, since this tumor may occur on a familial, or inherited, basis. In the syndromes of multiple endocrine neoplasia (MEN), the cancer may be associated with tumors in other endocrine organs, such as pheochromocytoma of the adrenals, parathyroid tumors and islet cell cancer ( see "Adrenal Gland" , "Parathyroid" and "Islet Cell and Other Pancreatic Carcinomas" ).
Unusual tumors that can arise in the thyroid gland include sarcomas, lymphomas, epidermoid carcinomas and teratomas. The thyroid gland can also be a site of metastasis from other cancers, especially cancers of the lung, kidney, breast, and melanoma.
