Epidemiology of Thyroid Cancer

Thyroid cancer is the most common endocrine malignancy. The major histologic subtypes for thyroid cancer is papillary, follicular, medullary, and anaplastic accounting for 80%, 10%, 5%, and < 2%, respectively. The incidence of thyroid cancer has been increasing exponentially with approximately 53,990 new cases being expected to be diagnosed in the USA in 2018. Because of the rising incidence and the good prognosis of thyroid cancer, prevalence rates are significantly higher than incidence with rates ranging from 0.03 to 36%. The mortality of thyroid cancer has remained relatively stable, despite an annual percent increase of 0.82% of rates in the USA from 1992 to 2012. Risk factors for thyroid cancer are also being reviewed in this chapter. Finally, the issue of overdiagnosis of thyroid cancer is addressed in the chapter. We believe that the increased incidence is likely the result of two coexisting processes: increased detection (apparent increase) and increased number of cases (true increase) due to unrecognized thyroid-specific carcinogens.