Introduction/Background Physiological changes in the mother’s body during pregnancy with the primary aim to support the fetus’s growth may also suspected to worsen the natural course of various malignancies with even poorer prognosis then in non-pregnant women. Though borderline ovarian tumors generally have an excellent prognosis, the risk of their progression during gestation remain has yet to be investigated. The purpose of this study was to assess the expression of epithelial-mesenchymal markers, angiogenesis and the extent of natural killers in samples of ovarian borderline tumors in pregnant and non-pregnant women.

Methodology Twenty three samples [13 from pregnant (30,5±4,7 years) and 10 from non-pregnant women (33,6±5,8 years)] were investigated morphologically and immunohistochemically with VEGF, CD31, CD105, CD56, E-cadherin, Vimentin, Mann-Whitney test was used for statistics.

Results Serous borderline tumors were diagnosed more frequently in pregnant and in non-pregnant women. In addition we diagnosed endometrioid and mucinous borderline tumors with welldiffentiated components in both groups. CD31 expression in pregnant women was significantly higher than that in non-pregnant patients (p<0.05) with the median number of CD31 positive vessels 28 (range 12–68) and 11 (range 4–19), respectively. There were no differences in the immunoreactivity of all other markers among both groups (p>0.05).

Conclusion Borderline ovarian tumors in pregnant women were characterized by an enhanced CD31 expression compared with non-pregnant patients. The increase level of CD31 expression in pregnant women is supposed to be enhanced be pregestrone activity through progestindependent angiogenesis activation. We speculate that the similarity in VEGF, CD-105, Ecadgerin, Vimentin, CD56 expression in pregnant and non-pregnant women’s indicates lack of stimulation in these agents-dependent signal pathways on borderline ovarian tumors progression complicating pregnancy

Disclosure Nothing to disclose.