Telomerase activity levels for evaluating the surgical margin in breast-conserving surgery. 
To evaluate the efficiency of measuring telomerase activity levels in clinical diagnosis, we performed a semiquantitative analysis of telomerase activity in breast tumors and compared the results with the histological findings.  Breast tissue adjacent to areas of cancer were also serially resected and checked for telomerase activity.  The amount of telomerase activity in the breast cancers ranged widely, from 0.36 to 1180 units/microg, with 31 of the 34 (91.2%) showing a value above 1.0unit/microg.  None of the normal breast tissues including mastopathy, and only 4 (23.5%) of 17 benign breast masses had values above 1.0unit/microg.  Telomerase activity was detectable in serial sections of adjacent tissues as far as 10mm from the macroscopic tumor margin with histologically detectable cancer cells.  Furthermore, telomerase activity was detectable in the scrape specimens obtained from the stump of the surgical margins for breast-conserving surgery, and this activity was in accordance with the histological findings.  These findings show that conducting a semiquantitative assay of telomerase activity is useful for evaluating the surgical margin in breast-conserving surgery.