Incidental thyroid malignancies in patients operated for hyperthyroidism

The incidence of thyroid cancer has increased in many countries in the last four decades, which might be attributed to the advances in diagnostic methods, an increase in pathological sampling, and, possibly, changes in the prevalence of risk factors (1). The most important etiological factor causing thyroid cancer is ionizing radiation, especially in childhood. Obesity, smoking, hypothyroidism, hormonal exposures, and some environmental pollutants are the other factors associated with thyroid cancer (1). However, the relationship between hyperthyroidism and thyroid cancer is still controversial. Hyperthyroidism is defined as hyperfunctioning of the thyroid gland; its prevalence in adults is approximately 1.2%. Graves’ disease (GD), toxic adenoma (TA), and toxic multinodular goiter (TMNG) are accepted as the most common causes (2). Until recently, hyperthyroidism was thought to be protective against the development of thyroid cancer due to the lower serum thyroid-stimulating hormone (TSH) concentration (2,3). However, thyrotoxicosis did not protect against incidental papillary thyroid cancer (4). The coexistence of thyroid cancer and hyperthyroidism varied widely from 1.6% to 21.1% (5). It is difficult to explain this variability. Another point of discussion is whether hyperthyroidism-related thyroid cancers are more aggressive (5,6). It is important to determine the incidence of malignancy in patients with hyperthyroidism and reveal the clinical behavioral pattern of incidental tumors. This is because the high incidence of malignancy may further emphasize the necessity of surgery among treatment options. Therefore, this study was conducted to evaluate the frequency of thyroid cancer in patients undergoing thyroidectomy due to different forms of hyperthyroidism and also examine the behavioral pattern of cancer in malignant cases. ABSTRACT