Thyroid cancer: Cancer of the gland in front of the neck that normally produces thyroid hormone which is important to the normal regulation of the metabolism of the body. There are 4 major types of thyroid cancer -- papillary, follicular, medullary, and anaplastic. The most common symptom of thyroid cancer is a lump, or nodule, that can be felt in the neck. The only certain way to tell whether a thyroid lump is cancer is by examining the thyroid tissue, obtained using a needle or surgery to obtain a biopsy.
Carcinoma of the thyroid gland is an uncommon cancer but is the most common malignancy of the endocrine (hormone making)system. Differentiated tumors (papillary or follicular) are highly treatable and usually curable. Poorly-differentiated tumors (medullary or anaplastic) are much less common, are aggressive, metastasize early, and have a much poorer prognosis. In spite of its role as a causal agent in common thyroid cancer radiation therapy both with radioactive isotopes (used as medicines) as well as with conventional radiation therapy and with surgery are essential in the management and hopefully the cure of thyroid cancer patients.
Thyroid cancer affects women more often than men, and usually occurs in people between the ages of 25 and 65 years. The incidence of this malignancy has been increasing. Patients with a history of radiation in infancy and childhood for benign conditions of the head and neck have an increased risk of cancer (and other abnormalities) of the thyroid. In this group of patients, malignancies of the thyroid may first appear anywhere between 5 and 20 or more years later. Persons who received radiation to the head or neck in childhood should be examined by a doctor every 1 to 2 years.
Radiation exposure as a consequence of nuclear fall-out has also been associated with a high risk of thyroid cancer, especially in children. Other risk factors for the development of thyroid cancer include a history of goiter, family history of thyroid disease, female gender, and Asian race.
The prognosis for differentiated carcinoma (papillary or follicular) is better for patients younger than 40 years without extension of the tumor beyond the thyroid. Age appears to be the single most important prognostic factor. An elevated serum thyroglobulin level correlates strongly with recurrent tumor when found in patients with differentiated thyroid cancer during postoperative evaluations.
Patients considered to be low risk by the age, metastases, extent, and size risk criteria include women younger than 50 years and men younger than 40 years without evidence of distant metastases. Also included in the low-risk group are older patients with primary tumors less than 5 cm and papillary cancer without evidence of gross extrathyroid invasion. Using these criteria, a retrospective study of 1,019 patients showed that the 20-year survival rate is 98% for low-risk patients and 50% for high-risk patients.