MMP2 and neoplasm: For SACC, many studies have shown that MMP2 and MMP9 were highly expressed both in the tumor and stromal compartments, and their expression is closely related to the malignancy of SACC, indicating that a variety of signal molecules could promote the invasion and metastasis of SACC by regulating MMP2/9 (Yang et al., 2012; Zhou et al., 2014).