MMP9 and esophageal squamous cell carcinoma: To further observe the distribution of staining of MMP9 and CD44 on FFPE-ESCC samples, two side-by-side comparisons taken from neighboring slide sections were stained using immunohistochemical staining, and the brown color was changed to either blue or red by adjusting hue to maintain contrast and brightness using Photoshop software, depending on where the section originated (blue for CD44 and red for MMP9).