These processes include the adhesion of tumor cells to adjacent cells, such as endothelial cells, neurons, astrocytes, and the ECM; changes in tumor cell morphology via reorganization of the intracellular cytoskeleton so that the tumor cell can more readily pass through the narrow spaces of the ECM; and diffuse migration into the normal brain tissues around the tumor mass with remodeling of the ECM via proteolytic degradation using matrix metalloproteinases, such as MMP-2 and MMP-9, to promote detachment from the adhered ECM and movement to a new site of adhesion [101,102]. This evidence concerns the gene MMP9 and neoplasm.