Latent carcinoma of the thyroid in Austria: A systematic autopsy study

Data concerning the incidence of latent thyroid carcinoma (LTC) in populati ons with endemic goiter are scarce. Despite the introduction of iodine goit er prophylaxis in the early sixties, iodine supply is still insufficient in Austria and goiter remains endemic. This is the first detailed study deali ng with epidemiological features of LTC at autopsy in Austria. A total of 1 18 thyroid glands were included in the study. The glands were serially sect ioned at 2- to 3-mm intervals, embedded in paraffin and histologically exam ined for the presence of LTC. In addition, the incidence and severity of ly mphocytic thyroiditis (LT) were evaluated. Ten thyroids were found to conta in LTC (8.6%). All were of the papillary type. The mean tumor dimension was 4.9 mm +/- 3.2, the smallest lesion measuring 1 mm. Only the largest tumor slightly exceeded the extent of a microcarcinoma and measured 10.5 mm. Mul tifocal disease was present in three cases (30%). The prevalence of latent papillary thyroid carcinoma (LPTC) was 6.6% (n = 4) in females and 10.5% (n = 6) in males. The mean age of the subjects with LPTC was 67.7 +/- 14.4 yr , range 37 to 77 yr. Goitrous thyroids were seen in 33 cases (28%): One gla nd was diffusely enlarged and 32 (27.1%) enlarged glands were nodular goite rs. The overall prevalence of LT was 30.5% (n = 36) and the only type of th yroiditis observed was focal lymphocytic thyroiditis (FLT). There was no co rrelation between the presence of LPTC and goiter, the presence of FLT and the subjects' age and sex. The incidence of LPTC in Austria is similar to t hat in nongoitrous regions. The adult population at large seems to be unifo rmly exposed to factors involved in the initiation and early growth of papi llary thyroid carcinoma (PTC). This suggests that the levels of iodine inta ke on ly play a minor role in the early phase of the carcinogenesis of PTC, but may be of some importance in the progression of LPTC to clinically evi dent PTC.