**5. Conclusions**

Our study provides solid evidence for a different BMI-1 expression in EOC and NEOC, corresponding to the differences in their etiopathogeny. The EOCs were largely characterized by a low BMI-1 expression in epithelial tumor cells, without a dominant expression profile in stromal cells. Epithelial BMI-1 is progressively increased alongside the tumor grade and strong stromal BMI-1 may be correlated to microenvironment modulation, supporting the rapid growth pattern and the recognized poor prognosis in a subcategory of EOC cases. The NEOCs were characterized by high BMI-1 expression in both the epithelial and stromal types of cells; therefore, BMI-1 expression could be regarded as an indicator of aggressiveness of this type of malignancies in general, and for HGSC in particular. Additionally, BMI-1 expression limited to the normal tubal surface epithelium and its lack in normal germinal/surface ovarian epithelium may support the hypothesis that many OCs are originating from the fallopian tube epithelium.

Nevertheless, the reported differences in BMI-1 expression in EOC and NEOC need to be further validated in a larger and homogenous cohort of study.

**Author Contributions:** Conceptualization, L.L., C.A. and I.-D.C.; methodology, L.L., R.A.B. and S.E.G.; software, R.A.B.; validation, L.L., C.A., S.E.G. and R.A.B.; investigation, L.L., R.A.B. and I.P.; writing—original draft preparation, L.L. and R.A.B.; writing—review and editing, C.A.; supervision, I.-D.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** No funding was received for this study.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of the "Grigore T. Popa" University of Medicine and Pharmacy, Ia¸si (12378/June 2015).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data used to support the findings of this study are available upon request to the authors.

**Conflicts of Interest:** The authors declare no conflict of interest.
