MMP-9 plays a crucial role in many aspects of cancer progression, such as growth, angiogenesis, tumor cell invasion, motility, and hematogenous, and lymphatic tumor dissemination.[24,33] MMP-9 is significantly upregulated in PCs and recurrent PAs compared to normal pituitary glands and in invasive compared to noninvasive PAs, suggesting that MMP-9 is associated with aggressive behavior and promotes malignant transformation of pituitary tumors. This evidence concerns the gene MMP9 and pituitary tumor.