Beschreibung: Background Ovarian serous carcinoma (OSC) is the most common ovarian epithelial malignancy. Despite new medical and surgical advances, the overall 5-year survival for OSC remains poor. There is an important need to determine diagnostic and prognostic markers for this disease. Eph receptors are the largest known family of receptor tyrosines characterised in humans. These receptors are involved in the development and progression of various diseases including cancer. EphB6 contains kinase domains that are altered in several conserved amino acids and is catalytically inactive. The aim of the present study was to correlate the immunohistological expression of EphB6 in a cohort of patients with epithelial ovarian tumours with clinicopathological parameters and survival. Methods In this study we examined the expression of EphB6 protein in 55 cases of OSC, 24 cases of benign ovarian serous tumours, 37 cases of serous borderline tumours and 20 cases with normal fallopian tubes by immunohistochemical staining with a polyclonal anti-EphB6 antibody. The relationship between EphB6 expression and pathological parameters was analysed. Kaplan–Meier survival function was used to analyse the prognosis. Results High expression of EphB6 was observed in 100% (20/20) of normal fallopian tube samples, 100% (24/24) of benign epithelial ovarian tumours, 78% (29/37) of ovarian serous borderline tumours and 18% (10/55) of OSCs (p〈0.001). The expression of EphB6 was significantly associated with grade (p〈0.001) and TNM stage (p=0.017). EphB6 expression was reversely related to Ki-67 (p=0.021). The survival analysis showed that patients with negative or weak expression of EphB6 protein had a poorer outcome than those with positive expression (p=0.046). Conclusions Our results show that EphB6 is a new biomarker for distinguishing high- and low-grade OSC, and may be a potential prognostic marker in OSCs.