RESUMEN
Olsztyn region (in the north of Poland) was classified as an iodine deficiency area with moderate endemic goiter prevalence. Following Chernobyl accident, the population had one of the highest radiation doses affecting thyroid. Aims of the study were to estimate the incidence of thyroid cancer and to determine its histopathological type. The register was carried out in Olsztyn region population including each newly diagnosed case of thyroid cancer in the calendar year. The personal data of patients were collected and processed on in computer. The incidence rate was calculated as the number of newly diagnosed cases in the calendar year per 100,000 inhabitants dependent on sex and age. The results were statistically evaluated. 242 newly diagnosed cases of thyroid cancer were registered including 8 young patients (up to 18 years of age) and 234 adults. The increase in the number of cancer cases was observed year by year. The predominant type of thyroid cancer was papillary carcinoma--66.8%. Follicular carcinoma constituted 17% of cases. A statistically significant increase of incidence rate was observed in women--from 2.8/100,000 to 11.1/100,000.