KLK5 and breast cancer: The statistically significant (p < 0.001) negative correlation of the KLK5 mRNA levels and the risk for breast cancer (crude odds ratio: 0.42, 95% CI: 0.26 - 0.67) in relation to the patients' age and tumor size demonstrates the independent ability of KLK5 expression quantification to discriminate the malignant breast tumor cases from those with benign lesions of the mammary gland.