Background Octamer-4 (Oct4) is a well known regulator of self-renewal in embryonic stem cells; it has been detected in several human cancers and may play a critical role in carcinogenesis.

Aims To assess the expression of Oct4 in epithelial ovarian tumours.

Methods Expression of Oct4 was evaluated by immunohistochemistry in 460 cases of various epithelial ovarian lesions as well as 35 cases of normal fallopian tube epithelium. The association between Oct4 expression and various clinical pathological parameters was analysed.

Results Oct4 expression was significantly increased from normal epithelium (both ovarian epithelium and fallopian tube epithelium) to benign and borderline cystadenoma to carcinoma in the serous lesion subgroup. Oct4 overexpression was associated with more advanced FIGO stage and higher histological grade in serous adenocarcinoma. Conversely, Oct4 expression did not differ among mucinous lesions or correlate with clinicopathological parameters in patients with mucinous adenocarcinoma.

Conclusion Results suggest that Oct4 expression may contribute to the initiation, promotion and progression of serous ovarian carcinoma; it might be a useful biomarker for the diagnosis and outcome prediction of serous ovarian carcinoma.