In the present work, we decided to investigate OPN expression in a large series (136 cases) of stage I NSCLC, in order to clarify the role that OPN plays in these tumours' biology, and to define its usefulness as a prognostic marker in identifying subsets of patients with a high risk of recurrence and who would be suitable for adjuvant and new therapies. This evidence concerns the gene SPP1 and neoplasm.