ESR1 and breast cancer: Furthermore, higher levels of MMP-11, MMP-9, and MMP-2 were observed in tissues from breast cancer patients with lymph nodes and estrogen receptor-positive, suggesting the critical role of MMPs in the pathophysiology of breast cancer.(33) Similarly, a recent study conducted in Egypt investigated the roles of MMP-2 and MMP-9 in women with breast cancer by measuring their plasma concentrations preoperatively and postoperatively.