Introduction/Background Ovarian cancer remains the most deadly gynecological malignant disease in developed countries. Basically, poor prognosis of this disease can be explained by the ineffectiveness of screening programs due to the lack knowledge of the ovarian cancer pathogenesis. Since pluripotent cells play a key role in the development of neoplastic epithelial changes, verification of the of their localization in transition zones (TZs) will help to determine the possibility of simultaneous existence of several potential sources for ovarian carcinoma development.

Methodology We investigated 165 tissue samples of the ovary and fallopian tube from patients with benign extraovarian pathology (uterine fibroids and adenomiosis) and 25 samples with high-grade serous ovarian carcinoma (HGSC) [(55 fimbriae, 25 parafimbrial zones (PFZ), 25 paraovarian zones (POZ), 35 samples of ovarian surface epithelium (OSE)]. Transition zones were taken separately for morphological assessment. Immunohistohemiscal investigation involved LGR5, NANOG, LNX9, CD117, CD44 and Oct4 assessment. Statistics was done with Student’s test with Boferroni correction.

Results LGR expressed in 38 fimbriae, 22 PFZ, 21 POZ, 32 OSEs; NANOG expressed in 25 fimbriae, 20 PFZ, 24 POZ, 35 OSEs; LHN9 expressed in 27 fimbriae, 19 PFZ, 19 POZ, 25 OSEs; CD 117 expressed in 30 fimbriae, 10 PFZ, 15 POZ, 11 OSEs. Statistically significant difference in progenitor markers expression were shown between TZs, OSE and fimbriae, as well as between normal epithelium and HGSC and between TZs and epithelial cells elsewhere (p<0,05).

Conclusion We investigated transitional zones of the uterine adnexa with progenitor cell markers and revealed that there is a significantly higher concentration of these cells in the transition zones where two types of the epithelia met. Thus, these zones can be a potential source (hot spot) for neoplasia development due to mutations in progenitor cells and further clonal expansion.

Disclosure Nothing to disclose.