We previously identified proenkephalin (PENK) methylation as a specific diagnostic biomarker for BC and demonstrated its clinical validity for BC detection by measuring PENK methylation in urine via quantitative methylation-specific polymerase chain reaction (PCR) qMSP) following linear target enrichment (LTE) (mePENK-LTE/qMSP test) [14], [15]. The gene discussed is PENK; the disease is breast cancer.