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Telomerase activity in thyroid neoplasms evaluated by the expression of human telomerase reverse transcriptase (hTERT).

BACKGROUND
The recent availability of a monoclonal antibody against human telomerase reverse transcriptase (hTERT) has enabled us to investigate the telomerase activity of tissue specimens more easily than by classical TRAP assay. In this study, we studied teromerase activity in thyroid tumors using this antibody.


MATERIALS AND METHODS
We immunohistochemically investigated hTERT expression in 166 thyroid neoplasms.


RESULTS
Normal follicular cells did not express hTERT. In papillary carcinoma, high hTERT expression was observed in 34.5% of cases and it was directly linked to stage and the presence of lymph node metastasis. In follicular carcinoma, 39.2% were classified as the high hTERT expression group, showing a significantly higher incidence than that in follicular adenoma, 9.8%. In anaplastic carcinoma, 73.7% were regarded as the high hTERT expression group, which was larger than the percentages in papillary and follicular carcinomas. We investigated the diagnostic usefulness of hTERT measurement for discriminating follicular carcinoma from adenoma. Its specificity and positive predictive value were high at 90.2% and 83.3%, respectively, while the sensitivity and negative predictive value were low.


CONCLUSION
These results suggest that: i) telomerase activity contributes to anaplastic transformation of differentiated carcinoma and ii) hTERT measurement may contribute to diagnosing follicular carcinoma, but whether it can be applied to preoperative diagnosis by fine-needle aspiration biopsy specimens remains unclear.