TELOMERASE ACTIVITY IN BENIGN AND MALIGNANT THYROID-DISEASES

Background. Telomerase, an enzyme associated with cellular immortality , is expressed by most malignant cells and is inactive in most normal somatic cells, with the exception of proliferative stem cells, male ge rm cells, and activated lymphocytes. The measurement of telomerase act ivity in clinically obtained tissue samples may provide useful informa tion as both a diagnostic and prognostic marker. In this study, we sou ght to determine whether telomerase activity might prove helpful benig n and malignant thyroid tumors. Methods. A modified, semiquantitative polymerase chain reaction-based telomeric repeat amplification protoco l assay was used for detection of telomerase activity in 59 samples ob tained at thyroidectomy, including 15 thyroid cancers, 22 benign thyro id diseases, and 22 adjacent normal thyroid tissues. Results. Four of 13 differentiated thyroid carcinomas (30%) and 2 of 2 medullary carcin omas (100%) expressed telomerase activity. Unexpectedly, we also detec ted activity in 3 of 22 (14%) adjacent normal thyroid tissues and 6 of 22 (28%) benign thyroid diseases. Pathologic review of the telomerase -positive benign specimens revealed that many contained extensive lymp hoid infiltrates with germinal centers (six of nine, 67%), as did two of four telomerase-positive papillary carcinomas. Conclusions. In cont radistinction to other epithelial carcinomas, telomerase does not appe ar to be frequently reactivated in differentiated thyroid carcinomas.