Etiology of thyroid cancer (C73) in Central and South America

Although the etiology of thyroid cancer remains unknown and the reasons for the worldwide increase in its incidence are not well understood, exposure to ionizing radiation in childhood [1] and a medical history of goitre or thyroid nodules have been consistently associated with an increased risk. The most common explanation for the marked increase in incidence over time has been the growing use of better diagnostic tools (i.e., ultrasonography, fine-needle aspiration biopsy, computed tomography, and magnetic resonance imaging) [2–4]. A striking increase in the incidence of thyroid cancer has been reported in the USA (particularly among women) since the 1970s due to the improved detection of small papillary cancers, although mortality from this malignancy has remained stable over the past 40 years [5, 6] and reports have shown that small papillary thyroid carcinomas may never progress to cause symptoms or death [2, 5]. Thus, the discrepancy between the increased incidence of and stable mortality from thyroid cancer could be explained by the identification of subclinical diseases (over-diagnosis) which in consequence would lead to an excellent prognosis [2, 7]. However, a rise simply caused by over-detection would not easily account for the increases observed in the developing world, where imaging techniques are less affordable. Thus, changes in risk factors may also be related in part to these higher rates. A brief review the potential risk factors associated with this malignancy is presented below.