Kaplan-Meier analysis of overall survival (OS) in which all patients with lung tumours were grouped according to the clinical classification (left, median survival SQCLC: 55 months; metHNSCC: 31 months) or proteomic classification (right, median survival SQCLC: 55 months; metHNSCC: 8 months) of the tumour as metHNSCC or SQCLC. The p value is from a log-rank test. Kaplan-Meier analysis of overall survival (OS) in which only the patients that were independent from the training cohort were grouped according to the clinical classification (left, median survival SQCLC: 84 months; metHNSCC: 35 months) or proteomic classification (right, median survival SQCLC: 84 months; metHNSCC: 5 months) of the tumour as metHNSCC or SQCLC. The p value is from a log-rank test. 