Tutorial: Thyroid Cancer
Thyroid cancer in the United States represents a small but significant number of patients in most referral centers. New diagnosis of thyroid cancer has increased in recent years and thyroid cancer may occur in 48,000 patients annually in the United States. The primary treatment for thyroid cancer is surgical. There are four main types of thyroid cancer. The most common is papillary carcinoma of the thyroid (about 85% of cases). The second most common is follicular carcinoma (about 10% of cases). Together, these two are often referred to as "well-differentiated" thyroid cancers. With appropriate treatment the prognosis for patients with well-differentiated thyroid cancer is generally excellent. Younger patients may have a higher rate of lymph node involvement. This sometimes involves more extensive surgery including total thyroidectomy and local lymph node resection. This has not been found to change long term survival rates.
Papillary carcinoma can be diagnosed preoperatively by the combination of ultrasound and fine needle aspiration biopsy. A patient with papillary carcinoma who has a mass less than 1 centimeter in one lobe of the thyroid can be treated with the removal of the lobe and the middle part of the thyroid (the isthmus). Patients who have a papillary thyroid cancer larger that 1 centimeter or who are older at presentation (especially males over 50) would most likely benefit from a total thyroidectomy. Your endocrinologist may make an additional recommendation for treatment with radioiodine (I-131) which would be given after you have healed from your thyroid surgery. This can often be done as an outpatient.
Papillary cancer is often thought to be "multicentric", that is, occurring simultaneously in several regions of the thyroid at the time of diagnosis. This is one of the reasons that a recommendation for a total thyroidectomy may occur at the time of diagnosis. Research continues to look at this issue, especially in low risk patients of younger age with smaller dominant masses.
Follicular cancer is the second most common form of thyroid cancer. It arises from the follicular cells of the thyroid and may be associated with benign masses such as goiters. Unlike papillary cancer, follicular cancer is hard to diagnose pre-operatively using fine needle biopsy (FNA). The diagnosis of follicular cancer requires a complete and thorough evaluation of the entire surgically removed specimen, therefore, the diagnosis may not be made for three to five days after surgery by the pathologists. The experience of the operating endocrine surgeon is paramount. The surgeon must use his or her best judgement as to the extent of resection necessary for a "follicular" lesion.
The minimal surgical resection for thyroid cancer should be the removal of a lobe and isthmus of the thyroid. Depending on the size and other features seen by the pathologist, a total thyroidectomy plus post-operative radioiodine (I-131) therapy are frequently recommended. Older males may have more aggressive disease, therefore they will more frequently require a total thyroidectomy.
Medullary carcinoma of the thyroid can present either as a non-familial circumstance, or as part of an inherited family syndrome known as multiple endocrine neoplasia (MEN I or II). MEN I syndrome involves patients with a combination of findings including a pituitary mass, hyperparathyroidism and a pancreatic mass. MEN II syndrome presents in families with adrenal masses (usually pheochromocytomas) parathyroid disease and medullary carcinoma of the thyroid. A patient who has a preoperative diagnosis or suggestion of medullary carcinoma of the thyroid may require additional preoperative evaluation for any of the familial disorders. Specifically, a workup for pheochromocytoma should be included. An undiagnosed pheochromocytoma can result in serious anesthetic complications if not evaluated and treated preoperatively.
Medullary carcinoma carries a poorer prognosis than the well-differentiated carcinomas. Some reports suggest that there is a 50% 5-year mortality in patients with diagnosed medullary carcinoma. The recognized surgical therapy for medullary carcinoma is total thyroidectomy and "a central lymph node" dissection. This incorporates removing all lymph nodes in the anterior part of the neck to evaluate possible metastatic spread. Depending on the particular case, more extensive surgery may be recommended.
Anaplastic carcinoma of the thyroid is an extremely serious and aggressive thyroid cancer which often results in the death of the patient by local recurrence and metastatic spread within several months of diagnosis. This is usually seen in older patients who have the rapid onset of a thyroid mass, pain and hoarseness. Thyroidectomy may be appropriate, but is not often helpful in stopping the rapid progression of such thyroid cancer and a tracheostomy may be in order to aid breathing. Anaplastic thyroid cancer is extremely rare involving less than 1% of patients with thyroid masses.
If you desire further information regarding thyroid cancer, we recommend reviewing the “Thyroid Gland” portion of the American Association of Endocrine Surgeons (AAES) Patient Education Site. Patients may find that many websites offer confusing or conflicting information regarding thyroid disorders. The AAES site offers reliable information.