Such biomarkers include matrix metalloproteinases (MMPs; including MMP2 and MMP9) which degrade extracellular matrix for enabling tumor invasion and epidermal growth factor receptor (EGFR), one subtype of ErbB receptors, which is expressed in PAs and regulates cell motility and adhesion, tumor invasion, angiogenesis and tumor cell proliferation (25). Here, MMP9 is linked to neoplasm.