Proliferative activity in thyroid tumors.

To clarify the proliferative activity of papillary thyroid carcinoma, the bromodeoxyuridine (BrdU) labeling index (LI) of 61 various thyroid tumors was investigated using an in vitro labeling technique and immunohistochemical staining with anti-BrdU monoclonal antibody. The mean LI (+/- standard deviation) of 31 papillary carcinomas, 12 adenomas, 10 adenomatous goiters, 3 follicular carcinomas, and 2 medullary carcinomas were 1.2% (+/- 1.3%), 0.6% (+/- 0.3%), 0.7% (+/- 0.6%), 1.5% (+/- 2.2%), and 0.7% (+/- 0.6%), respectively. The LI of the papillary carcinomas ranged from 0.1% to 4.6%, and approximately 66% of these showed less than a 1% similarity with almost all benign tumors. However, the LI of the two malignant lymphomas and the one anaplastic carcinoma were more than 13%. When the LI of the papillary carcinomas was compared with their various prognostic factors, there was no correlation with tumor size, nodal status, or morphologic features. However, the patients who were 50 years of age or older tended to have relatively high LI, and the LI of the papillary carcinomas correlated with patient age. According to these results, the biologic characteristics of papillary carcinomas vary with age and high proliferative activity may contribute to the poor prognosis of this tumor in elderly patients.