[Focal lymphocytic thyroiditis and iodized salt prophylaxis. Comparative studies on goiter specimens at the Institute of Pathology of Zurich University].

Hashimoto's thyroiditis is rare in endemic goiter areas. Recent investigators, however, claim an overall increase in its occurrence even in goiter areas. According to some reports the rising incidence of focal lymphocytic thyroiditis may be correlated to iodine prophylaxis. Consequently, 675 thyroid specimens were examined for the presence of focal lymphocytic thyroiditis. They had been collected at our Institute of Pathology over two 1-year periods 25 years apart (1954 and 1979), when iodine content in table salt differed considerably. Cursory examination seemed to confirm the original claim, since non-nodular tissue exhibited focal thyroiditis in 20.7% and 31.2% of cases in 1954 and 1979 respectively. Morphometric analysis, however, produced equal results for both years as far as depth of infiltration was concerned. Focal thyroiditis particularly affects non-nodular parenchyma, which was found to take up 1.5 times more area in 1979 than in 1954. Thus, infiltrates located between nodules appear more frequently as routine sections pass through larger areas of non-nodular parenchyma. However, changes in the absolute frequency or extent of focal lymphocytic thyroiditis in goiters under increasing iodine prophylaxis could not be demonstrated.