We have reviewed the literature to clarify if routine invasive mediastinal staging is indicated also in Stage I elderly patients screened with PET/CT scan. Nineteen papers were chosen to answer the question. Occult pN2 disease was < 10% in five papers; between 10-16% in four papers; and > 16% in four papers.Significant risk factors for occult pN2 disease are the SUV value of primary tumor (seven papers), central tumor (four papers), tumor > 3 cm (five papers), adenocarcinoma histology (five papers) and cN1 disease(two papers). Two papers found that unexpected pN2 patients had a better survival than cN2 patients operated after induction therapy. Invasive mediastinal staging is recommended also in cN0 patients with central tumor or with peripheral tumor > 3 cm
