Increased MMP‐9 expression is associated with all stages of lung cancer and poor prognosis, but has also been detected in mild squamous dysplasia, where cells expressing MMP‐9 moved through disrupted basal membranes with colocalized collagen and MMP‐9 (Galateau‐Salle et al., 2000; Wei, 2023). This evidence concerns the gene MMP9 and lung cancer.