Cystatin C (CST3) is the most abundant extracellular inhibitor of cysteine proteases, with high concentrations of this protein found in biological fluids and practically all organs of the body, including the urinary bladder.32 In this study, we found that CST3 expression was significantly associated with favorable patient outcomes, including overall survival, disease-free survival, and progression-free interval, consistent with previous findings on breast cancer,58 but not on non-small cell lung cancer.59 Here, CST3 is linked to breast carcinoma.