Thyroid carcinoma in benign thyroid diseases. An analysis from minute carcinoma.

The relative frequency of thyroid carcinoma in benign thyroid diseases such as toxic diffuse goiter (toxic goiter), adenomatous goiter (goiter), adenoma, and chronic thyroiditis (thyroiditis) was studied using 3,219 surgically removed thyroid glands. Coexistence of carcinoma and benign diseases was found in 257 glands. Among them, 157 glands had minute carcinoma (diameter of cancer nodule is smaller than 10 mm) and 100 glands had advanced carcinoma (larger than 10.1 mm in diameter). The incidence of carcinoma including minute carcinoma was 29.4% in goiter (98/333), 21.0% in thyroiditis (11/53), 8.6% in adenoma (55/638), and 5.3% in toxic goiter (98/1852). Chi-square test also revealed that the rate of carcinoma not only advanced carcinoma but also minute carcinoma was higher in goiter than in the other diseases (P less than 0.01, respectively). Among the patients aged under 39, the incidence of advanced carcinoma and minute carcinoma in thyroiditis were the highest, respectively (83% and 100% in thyroiditis, 9.0% and 11.4% in goiter, 2. 6% and 1.9% in adenoma, and 0.7% and 3.4% in toxic goiter), however, among the patients aged over 40, they were secondary lower and the lowest, respectively (19% and 16.8% in goiter, 5.2% and 7.5% in adenoma, 4.2% and 6.7% in thyroiditis, and 1.4% and 7.5% in toxic goiter). We concluded that adenomatous goiter accompanies carcinoma more frequently than other benign thyroid diseases and the high incidence of carcinoma in chronic thyroiditis is probably due to a preoperative selection of the patients.