EP21.20: Decidualisation of endometrioma versus borderline ovarian tumour in pregnancy

A 31-year-old patient was examined at 13th week of pregnancy. The ultrasound examination revealed a tumour of the right ovary with suspicious hypoechoic content and peripherally visible hyperechoic papilations with moderate vascularization. The ultrasound image of the tumour resembled a decidualising endometrioma (dimensions 30,4mm x 17,7mm x 25mm). Differential diagnosis including borderline serous ovarian tumour or early stage of ovarian cancer had to be considered. There was lack of information of possible previous presence of endometrioma in this ovary. It was decided to undertake intensified supervision of more frequent check-ups of the ovary during routine pregnancy visits. The ultrasound image of the lesion did not change during course of pregnancy. The patient had a natural labour in the 40th week of pregnancy. During routine check-up one month after delivery, previously observed tumour was still present. Ca-125 marker at that moment was within normal ranges (11,5 U/ml). Because of persistent suspicious picture of the ovary it was decided to remove the tumour during laparoscopic surgery. The obtained material was sent for histopathological examination, the result of which was consistent with borderline tumour. Further treatment was carried out in accordance with oncological recommendations. The described case indicates similarities between decidualization of endometrioma and ultrasound picture of serous borderline tumour. Moreover the case underlines need to evaluate adnexa during routine 13th week examination in pregnancy. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.