In a retrospective analysis among breast cancer patients, which analyzed the effect of anesthetic technique on MOR expression, the authors found that general anesthesia with opioid analgesia increased MOR expression in the resected tumor compared to anesthetic technique with locoregional analgesia (30), These results support the hypothesis that the opioid receptor genetic footprint varies with tumor type. The gene discussed is OPRM1; the disease is breast carcinoma.