Trends in thyroid cancer incidence in Sweden, 1958–1981, by histopathologic type

Abstract

Time trends in the incidence of malignant neoplasms of the thyroid were examined for Sweden for the period 1958–81, 5, 838 cases being studied. Autopsy‐diagnosed cases were excluded. Mean annual changes in the age‐standardized rates over this period were 1.9% and 1.2% for women and men, respectively, for all thyroid carcinomas combined; 4.9% and 2.1 % for papillary carcinoma; 0.9% and 2.1 % for follicular carcinoma; and − 1.0% and −2.1 % for anaplastic carcinoma. Age, period and cohort models were fitted. There was a progressive increase in papillary cancer incidence for cohorts born since 1919. This increase cannot be satisfactorily explained as an artefact of trends in classification, and probably reflects a real increase in incidence. A less marked increase was seen for follicular cancer, and there was a decline for cohorts born since 1939. While the risk of papillary and anaplastic carcinoma was lower in iodine‐deficient areas, follicular cancer risk was twice as high in these areas, for men only. There was a steady decline of anaplastic cancer in both sexes after 1965, largely attributable to a decline in cohorts born since 1924.