Previous studies revealed that PAI‐1 produced by cancer cells was associated with cancer progression and prognosis in various malignancies.32, 33, 34 On the other hand, we previously reported that host, but not tumour, PAI‐1 is important in lung cancer progression in vitro and in vivo.15 In this present study, we showed that the high level of host PAI‐1 expression in the tumour stroma was associated with tumour size and the TNM stage using immunohistochemical analysis of lung cancer tissue. This evidence concerns the gene SERPINE1 and cancer.