Global variation in the pattern of differentiated thyroid cancer

Background: The prevalence of differentiated thyroid cancer (DTC) is increasing worldwide. Iodine deficiency is a risk factor for follicular thyroid cancer (FTC). We compared DTC subtypes in an iodine-deficient country with a developed country. Methods: A retrospective review of thyroid cancer at tertiary centers in West Africa and the United States. All patients diagnosed with thyroid cancer from 1980 to 2004 were retrieved from the West African Center's Cancer Registry Database. The study period was divided into two groups: 1980 to 1989 and 1990 to 2004. In the American center, a review of patients undergoing surgery for thyroid cancer from 1997 to 2008 was performed. Results: At the African institution, 322 patients underwent thyroidectomy for cancer from 1980 to 2004. Overall, 31.5% had papillary thyroid cancer (PTC), and 30.3% had FTC. From 1980 to 1989, 27.3% had PTC and 35.8% had FTC. From 1990 to 2004, 35.7% had PTC and 24.8% had FTC. At the American institution, 105 patients underwent surgery for thyroid cancer from 1997 to 2008; 79% had PTC and 7.6% had FTC. Conclusions: FTC is still common in developing countries, whereas PTC is the predominant subtype in developed countries. Efforts to decrease iodine deficiency may improve outcomes by changing to a less aggressive subtype.