Absence of YAP1 protein expression is associated with tamoxifen resistance in the randomised patient cohort. (a) Kaplan-Meier analysis of all ER+ patients, both treated (tamoxifen) and untreated. Absent YAP1 expression is correlated to a decreased recurrence-free survival. (b) In the ER- subgroup both absent and strong YAP1 expression correlated to a worse outcome. (c) Analysis of the untreated patient cohort of ER+ patients indicates no prognostic value of YAP1. (d) Analysis of the tamoxifen treated patient cohort of ER+ patients suggests predictive value of absent YAP1. (e) ER+ patients with tumours scored as weak, intermediate or strong YAP1 expression do significantly better when treated with tamoxifen compared to the untreated control group whereas (f) ER+ patients with YAP1 scored as absent do not benefit from tamoxifen. RFS = recurrence-free survival.