[Differentiated thyroid carcinoma in previously manifested autoimmune thyroid disease]

Autoimmune thyroid diseases are frequently associated with differentiated thyroid carcinomas. The role of autoimmune phenomena in the origin and clinical course of coexisting papillary and follicular carcinomas is still controversial. In Graves' patients, the prevalence of palpable thyroid nodules is 15.8%, and by using ultrasonography, the prevalence increases to 33.6%. Since the malignancy rate of palpable thyroid nodules in Graves' patients is 16.9%, approximately threefold higher than in general population, it seems that a thyroid nodule diagnosed in Graves' patients is at higher risk for malignancy. In addition, radioiodine therapy for Graves' disease was found to be associated with increased incidence of thyroid cancer in some studies. These studies however, were not able to confirm the carcinogenic effect of radioiodine therapy since the late growth of occult carcinomas could not be excluded. The frequency of the association of Hashimoto's thyroiditis and differentiated thyroid carcinomas is approximately 30%. The presence of coexistent Hashimoto's thyroiditis does not affect the diagnostic evaluation and management of papillary thyroid cancer. The frequent presentation of differentiated thyroid carcinomas in Graves' disease and Hashimoto's thyroiditis opens the possibility that some mutual pathogenethic mechanisms might be involved in the development of these diseases.