MMP9 and myeloid sarcoma: The ratio between MMP-9 and MMP-2 was proposed as a serum marker to monitor the progression of liver disease, and the ratio between MMP-2 and MMP-9 was associated with poor response to chemotherapy in osteosarcoma in two previous studies [39, 40]; however this is the first time that the ratio between the active forms of MMP-9 and MMP-2 was calculated in MS patients, and for this reason further studies are required to investigate the biological significance of the imbalance between serum levels of gelatinases.