KLK3 and breast cancer: It was demonstrated that 44% of women with breast cancer and 58% of women with benign breast disease had serum free PSA as the major molecular form, whereas normal women had PSA bound to α1-antichymotripsin as the major molecular form, and it was suggested that the ratio of free PSA/bound PSA might have value for diagnosis of breast diseases including breast cancer (Borchert et al, 1997).