P-320 Ovarian tissue attached to stripped endometriomas: transforming the collateral damage to a potential source for oocyte preservation?
Authors: De Koning R , Blikkendaal M , Chuva de Sousa Lopes S , Van der Meeren L , Cheng H , Jansen F  W , Lashley L 
Published: July 2024

Abstract

Study question
To determine (antral) follicle density in the ovarian cortex tissue attached to stripped endometriomas and patient- and surgical characteristics affecting this density.

Summary answer
Ovarian tissue attached to stripped endometriomas offers a non-invasive source for antral follicles. Research with fresh tissue is necessary to further asses the quality.

What is known already
Ovarian endometriosis is associated with diminished ovarian reserve due to the disease itself as well as damage caused by excisional surgery, which may result in subfertility. When resecting endometriomas with the stripping technique, in the majority of cases, a thin line of adjacent ovarian cortex is attached to the endometrioma. Data regarding density and maturation of the follicles in this tissue are conflicting in previous publications. This study aims to quantify and characterise follicles and in particular antral follicles in ovarian tissue surrounding resected endometriomas as these may serve as a potential oocyte source for in vitro maturation (IVM).

Study design, size, duration
A retrospective cohort study was conducted at the Leiden University Medical Centre and the Endometriosis in Balance endometriosis expertise centre in Haaglanden Medical Centre (The Netherlands). Pathology slides of patients (≤50 years) that underwent uni- or bilateral endometrioma resection between 2011 and 2021 were analysed for the presence of follicles.

Participants/materials, setting, methods
Histological slides of previously removed endometriomas were assessed according to maturation and follicular density. Gougeon’s original follicle classification was modified by adding additional intermediate stages. Immunofluorescent staining of antral follicles in a subset of endometriomas was also performed.

Main results and the role of chance
In 90 out of 96 included endometriomas (93.7%), ovarian tissue attached to the cyst wall was observed. 1944 follicles at different maturation stages were identified (3 follicles/mm3). Follicle density was negatively associated with age (p &lt; 0.001). Antral follicles (&lt;7mm diameter) were present in the ovarian tissue attached to 35 endometriomas (36.5%) derived from younger patients compared to endometriomas where none were detected (30 versus 35 years, p = 0.003). Antral follicle density was 1 follicles/mm3. Based on immunofluorescence, healthy antral follicles were identified in 2 out of 4 examined endometriomas.

Limitations, reasons for caution
Tissue analysis was constrained by number of available pathology slides per patient, not fully representing the follicle distribution in the removed ovarian tissue. Immunofluorescence was performed on paraffin embedded tissue derived from a small number of endometriomas. Future research with fresh tissue is necessary to further assess viability.

Wider implications of the findings
Ovarian tissue attached to stripped endometriomas holds potential as a non-invasive source for antral follicles. In theory, application of IVM could be an interesting alternative fertility preservation option in young patients with endometriomas who undergo cystectomy in order to transform the surgical collateral damage to a potential oocyte source.

Trial registration number
not applicable