MMP9 and thymoma: Patients with and without thymoma did not differ with respect to age (p = 0.29), AChR antibodies serum levels (p = 0.18), disease duration (p = 0.89), gender (p = 0.36), as well as with regard to plasma levels of MMP-9 (p = 0.23), MMP-2 (p = 0.79), TIMP-1 (p = 0.69) and TIMP-2 (p = 0.79).