Although still rare, the incidence of thyroid cancer is increasing. In this longitudinal study over 12 years from a large cancer registry, Kent and colleagues used the Ontario Cancer Registry to identify 7422 cases of differentiated thyroid cancer from 1990 to 2001. Their results show the jump in the incidence rate of this type of thyroid cancer was 146% over the 12-year period, or an annual increase of 13% per year.In their study, the authors found that small (less than 2 cm), subclinical tumours accounted for the increased incidence, suggesting that advances in medical imaging, rather than a change in disease pattern, may be responsible for the increase.
