The IHC optical density score of MMP-9 in eutopic endometrium obtained from women with endometriosis was significantly higher (1.85 ± 0.26 IHC optical density score) than that in the eutopic endometrium obtained from women without endometriosis (1.3528 ± 0.067, p = 0.001). The gene discussed is MMP9; the disease is endometriosis.