In an earlier study, we demonstrated that Gal-9 mRNA is expressed in ectopic implants and peritoneal cells, and that serum Gal-9 concentrations are significantly elevated in patients with endometriosis, with excellent diagnostic performance (AUC of 0.973, sensitivity of 94%, and specificity of 93.8%) [18]. This evidence concerns the gene LGALS9 and endometriosis.