Significant correlation of telomerase activity in thyroid papillary carcinomas with cell differentiation, proliferation and extrathyroidal extension.

Telomerase activity was examined by telomeric repeat amplification protocol assay in thyroid disease states, including adenomas and carcinomas, and correlated with clinicopathological features. Of a total of 26 papillary carcinomas, 16 cases (61.5%) were positive, with the poorly differentiated subtype being predominant (P < 0.05). A significantly more shortened terminal restriction fragment length (P < 0.05), higher incidence of extrathyroidal extension (P < 0.001), and more elevated Ki-67 labeling indices (P < 0.002) were also found in telomerase-positive than in telomerase-negative papillary carcinomas. Of four follicular carcinomas, 3 cases (75.0%) were positive. Positive telomerase activity in follicular adenomas (9/23 cases, 39.1%) and lymphocytic thyroiditis (12/22 cases, 54.5%) appeared to be mainly caused by infiltrating lymphocytes. However, three cases of atypical adenoma with relatively increased Ki-67 labeling indices were positive, suggesting a possibility of malignant potential. The good correlations with extrathyroidal invasiveness, Ki-67 labeling indices and poor differentiation of papillary carcinomas, established by multivariate analysis, suggest that this parameter might have potential application in the estimation of tumor progression and prognosis, and in clinical management.