INTRODUCTION: We developed one of the first clinicopathological prognostic nomograms for resected squamous cell lung cancer (SQLC). Herein, we validate the model in a larger multicenter cohort and we explore the impact of adjuvant/neoadjuvant treatment (ANT).METHODS: Resected SQLC patients from January 2002 to December 2012 in six institutions were eligible. To each patient was assigned a prognostic score based on those clinicopathological factors included in the model (age, T-descriptor according to TNM 7th edition, lymph nodes, grading). Kaplan-Meier analysis for disease-free/cancer-specific/overall survival (DFS/CSS/OS) was performed according to three-class risk model. Harrell's C-statistics were adopted for model validation. The effect of ANT was adjusted with propensity score (PS).RESULTS: Data from 1,375 patients was gathered (median age: 68 years; male: 86.8%; T-descriptor 1-2/3-4: 71.7%/24.9%; nodes negative/positive: 53.4%/46.6%; grading 1-2/3: 35.0%/41.1%). Data for survival analysis was available for 1,097 patients. With a median follow-up of 55 months, patients at low risk had a significantly longer DFS versus intermediate (HR 1.67, 95% CI 1.40-2.01) and high risk (HR 2.46, 95% CI 1.90-3.19), as well as for CSS (HR 2.46, 95% CI 1.80-3.36; HR 4.30, 95% CI 2.92-6.33) and OS (HR 1.79, 95% CI 1.48-2.17; HR 2.33, 95% CI 1.76-3.07). A trend in favor of ANT was observed for intermediate/high risk patients, particularly for CSS (p=0.06; 5-year CSS 72.7% versus 60.8%).CONCLUSIONS: A model based on a combination of easily available clinicopathological factors effectively stratifies resected SQLC patients in three-risk classes.