Occult thyroid carcinomas in the region of Minsk, Belarus. An autopsy study of 215 patients.

Thyroid glands from 215 patients, aged 19 to 88 years, without known thyroid disease, were serially sectioned at 2-3 mm intervals and microscopically examined for occult disease. Glands were normal in 32.5%, while nodules were observed in 60% and adenomas in 13%. Carcinomas were found in 20 cases (9.3%): occult papillary carcinomas in 19 (8.8%) and one medullary carcinoma. No carcinomas were found in the thyroids of 15 patients less than 40 years of age. There were no significant differences in frequency of occult carcinomas between female and male patients and, for patients over 40 years, with increasing age. Of the 19 papillary tumours more than one focus was found in six cases (a total of 28 foci). The diameter of 27 of these tumours was less than or equal to 5 mm (96.4%), with one exception (diameter 6.3 mm). These findings were compared with those obtained in 86 thyroid glands of children surgically resected for carcinomas between 1986 and 1991. Only 10 of these tumours (11.6%) were less than or equal to 1 cm. These tumours, however, were significantly larger than the occult papillary carcinomas and their morphological features were quite different. Our results are discussed with regard to the possible role of factors other than irradiation due to the nuclear accident at Chernobyl, and the observed sharp numerical increase of thyroid carcinomas in children of the Republic of Belarus after this event.