It was also shown that there was a statistically significant increase in MMP-9 area expression in the stroma of the endometrium in the case of extragenital endometriosis (p < 0.05) in comparison with the control group at all stages of endometriosis (p = 0.004; p = 0.006; p = 0.003; p = 0.003 for stages I, II, III, and IV, respectively) (Figure 3a). The gene discussed is MMP9; the disease is endometriosis.