Prevalence of well-differentiated thyroid cancer in the Split – Dalmatia Country in the period from 2011. to 2015Diploma Thesis Title: Prevalence of well-differentiated thyroid cancer in the Split – Dalmatia Country in the period from 2011. to 2015. Objectives: To analyze epidemiologic characteristics of patients with well differentiated thyroid carcinoma and histological types of the former in University Hospital of Split from 2011. to 2015. Materials and Methods: A retrospective epidemiologic research has been done. Patients’ samples included all patients who are referred to thyroid surgery within the Clinic for Ear, Nose, and Throat Diseases with Head and Neck Surgery at KBC Split. Age (years), sex (male/female), referral diagnosis and histological type of carcinoma were determined. Results: Records of 1361 patients were analyzed of which 514 were diagnosed well differentiated thyroid gland cancer. Average age of patients was 55.61 years. The most common histological type of thyroid carcinoma was papillary (92.60) and the second most common was follicular carcinoma (7.40%). The ratio of women and men with papillary cancer is 3.81: 1 (377: 99), while the ratio of women and men with follicular type 3.75: 1 (30 : 8). Comparing the values from the research conducted in the period from 1997. to 2006. and the incidence in the period from 2011. to 2015. a statistically significant increase in the incidence of illness is obtained; T (669) = 19.96, p <0.01. Conclusion: In Clinical Hospital Center Split most patients with well-differentiated thyroid gland cancer were female. During period from 2011. to 2015. there was a rise in diagnosed cases and a change in thyroid cancer incidence was reported. The most common histological type is papillary carcinoma. In female population there is a discrete drop in incidence until 2015. when a sudden increase in the number of diagnosed thyroid carcinoma has been reported. The frequency of thyroid cancer in men has increased.