PCSK9 and breast disorder: Interestingly, upon tumor regression, PCSK9 levels returned to almost normal, akin to the control level.331 This observation is in harmony with a recent clinical study involving 46 cases, which suggested that PCSK9 levels could escalate in proportion to the severity of breast disease, with the lowest levels found in benign disorders while the highest in stage III breast cancer.333 Such evidence accentuates the potential utility of PCSK9 as a diagnostic and prognostic biomarker in breast cancer.