OBJECTIVETo investigate telomerase gene expression in precancerous mammary lesion, such as atypical ductal hyperplasia and breast cancer and to study the relationship between expression and malignant transformation.

METHODSExpression of human telomerase genes (hTR) and human reverse transcriptase gene (hTRT) in 76 cases of mammary tissue was evaluated using in situ hybridization and included 50 cases of mammary hyperplasia, 6 of which were benign hyperplasia, 9 were mild atypical hyperplasia, 12 were moderate atypical hyperplasia, 23 were severe atypical hyperplasia and 26 were mammary cancer.

RESULTSThe expressions of hTR and hTRT mRNA were much weaker or negative in benign hyperplasia (16.6%, 0), weak to mild moderate in atypical hyperplasia (22.2%, 11.1%, 33.3%, 25.0%), strong in severe atypical hyperplasia (60.9%, 52.1%), and significantly strong in mammary cancer (88.5%, 80.8%). The difference between mild-moderate atypical hyperplasia, invasive ductal carcinoma and severe atypical hyperplasia was significant (P < 0.05) and the difference between severe atypical hyperplasia and intraductal carcinoma was not significant (P > 0.05).

CONCLUSIONTelomerase genes (hTR and hTRT) expressions are related to the transformation of atypical hyperplasia. Activated telomerase may play a role in mammary cancer development.