Association Between Metabolic and Bariatric Surgery and Melanoma Risk: A Systematic Review and Meta-analysis of Observational Studies.

Metabolic and bariatric surgery (MBS) has been associated with a reduced incidence of various cancers. Yet, its potential impact on melanoma, the most lethal form of skin cancer, remains unclear. This systematic review and meta-analysis aimed to explore associations between MBS and melanoma risk. We searched MEDLINE, Embase, and Cochrane for studies that compared MBS to non-MBS patients and reported the incidence of melanoma in both groups up to December 2025. The primary outcome was the risk of developing melanoma. A restricted maximum likelihood random-effects model was used to calculate risk ratios with 95% confidence intervals. Ten studies were included, encompassing 2,310,128 patients, of whom 445,947 (19.3%) underwent MBS. The overall incidence of melanoma was 0.11% in the MBS group (516 / 445,947) and 0.24% (4,498 / 1,864,181) in the control group. Slightly lower melanoma risk was observed in the MBS group, although the difference did not reach statistical significance (risk ratio 0.78; 95% CI 0.52 to 1.16; p = 0.222; I² = 85%). By synthesizing the largest body of evidence to date and focusing on melanoma as the primary outcome, this study provides a comprehensive assessment of the association. Considering the rarity of the outcome, the substantial heterogeneity, and the very low certainty of evidence from observational studies, further large-scale studies are warranted to better define the association between MBS and melanoma risk.