OC04.05: Ultrasound imaging and hysteroscopy findings in patients referred with atypical placental site nodule to a tertiary gestational trophoblastic centre

Atypical placental site nodule (APSN) is a rare histological intermediate between benign placental site nodule (PSN) and malignant epithelial trophoblastic tumour (ETT) and may progress to placental site trophoblastic tumour (PSTT) or ETT. Patients diagnosed with APSN are offered a hysterectomy in view of its 15% risk of progression to these malignant conditions, or, if that is not accepted, interval monitoring with hysteroscopy and endometrial biopsy. The aim of this study was to assess if there are any ultrasound or magnetic resonance imaging findings at initial presentation in APSN. A retrospective review of all cases of APSN referred to a Tertiary Gestational Trophoblastic Centre in London between May 2017 and December 2023 was conducted. Women diagnosed with APSN were all offered a hysteroscopy and endometrial biopsy at the tertiary centre, along with ultrasound and MRI imaging. Information on hysteroscopy and endometrial biopsy findings, parity, fertility wishes, USS pelvis, MRI pelvis and MRI head was collected. In this study, 24 women were diagnosed with APSN and thus referred to a Tertiary Centre. Of these women, on subjective hysteroscopic assessment, 44% had a normal endometrial cavity, 11% had endometrial polyps, 22% had a focal endometrial lesion, 11% had residual dead placental tissue and 11% had a thickened endometrium. Histology showed 50% had no evidence of malignancy/benign endometrial tissue, 29% had APSN, 4% had ETT, 8% had residual trophoblastic tissue, 4% had hyalinised placental site nodule, and 1 case was non-diagnostic. Ultrasound imaging in these patients reported no endometrial or myometrial pathology in 92% of the cases. All pelvic MRIs in these patients were normal. 75% of women had not completed their family at time of diagnosis. This study suggests that current ultrasound imaging techniques do not replace histological diagnosis in cases of APSN.