Determination of growth fractions in benign breast disease (BBD) with monoclonal antibody Ki-67.

Certain types of benign breast disease (BBD) carry an increased risk of malignancy. Several morphological criteria such as an atypia score are used to define this group, and the use of a kinetic parameter may provide additional information. Therefore, the growth fractions of 120 benign breast lesions were determined using the monoclonal antibody Ki-67. The values obtained range from 0.3% to 10.8% (average 3.1% +/- 2.2%) compared to breast carcinomas with an average of 15.3% +/- 10.1%, range 0.8% to 47.8%. All specimens were classified using the terminology of Azzopardi. The prevailing histological entities were cystic disease, fibroadenoma, and blunt duct adenosis. Between these groups no differences in growth fractions were observed. Postmenopausal patients had slightly lower values than premenopausal women. Further prospective studies are needed to evaluate whether those cases of BBD with a high number of Ki-67 positive cells have an increased risk of breast cancer, independently from conventional histological classifications.