KLK3 and breast fibrocystic disease: In another study (Black et al, 2000), it was demonstrated that the percentage (20%) of breast cancer patients with free PSA as the predominant molecular form (>50% of total PSA) in serum was significantly higher than that of healthy women (3%) or women with benign breast disease (4%), and it was stated that although free PSA as the predominant molecular form has high specificity (96%), its clinical utility is limited due to low sensitivity (20%).