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Thyroid Cancer: Overview and Risk Factors

Thyroid cancers are uncommon, accounting for less than 1% of all cancers. However, incidence has risen significantly during the past half century, possibly the result of radiation therapy to the head and neck used to treat benign childhood conditions in the mid–1900s.

Patients usually present with a solitary thyroid nodule. Although most nodules are benign, all patients with a thyroid nodule should be evaluated for thyroid cancer. Other symptoms that raise suspicion of thyroid cancer include hoarseness, dysphagia or odynophagia, and adenopathy.

The majority of thyroid cancers are papillary or follicular carcinomas. Medullary carcinoma and anaplastic carcinoma are far less common. Papillary and follicular carcinomas are well–differentiated tumors that respond well to treatment, with cure rates exceeding 90%. Medullary carcinoma, which accounts for just 5% of cases, is a cancer of the calcitonin–producing C cells of the thyroid that may be associated with multiple endocrine neoplasia type 2 (MEN 2) syndromes. Anaplastic carcinoma is a rare but aggressive cancer with a very poor prognosis.

Risk Factors

Female gender. Nearly three–fourths of thyroid malignancies occur in women, making this cancer the eighth most common female malignancy.

Radiation exposure. Head and neck radiation, especially during infancy, is a strong risk factor for all thyroid cancers.

Genetics. Relatives of thyroid cancer patients have a 10–fold greater risk. In addition, medullary carcinoma may be inherited, either with MEN 2 syndromes or as an isolated familial disease. Rearrangements of the RET and TRK genes are found in some papillary carcinomas.


Thyroid Cancer: Diagnosis and Treatment >>