The analysis of the MMP-9 area expression in the glandular component of the endometrium revealed a statistically significant increase (p < 0.05) in comparison with the control group at all stages of endometriosis (p = 0.002; p = 0.002; p = 0.002; p = 0.003 for stages I, II, III, and IV, respectively) (Figure 3b). This evidence concerns the gene MMP9 and endometriosis.