Objective:To investigate the value of the clinical application of telom-erase activity by fine needle aspiration from breast masses for preoperative diagnosis of breast cancer in order to provide scientific basis for its practical clinical application. Methods: 85 patients with breast masses were aspirated by fine needles in the study. The samples obtained by aspiration were detected with telomerase activity by telomeric repeat amplification protocol (TRAP) assay and observed with cytomorphology by microscope respectively. The sensitivity, specificity and Youden's index of the two detective methods in diagnosis for breast cancer were compared respectively while postoperative paraffin slice pathologic results were considered as the final standard. Results:Compared with cytomorphology by microscope,preoperative telomerase activity detection's specificity which is 73.9% versus 82.6%(P