Retroperitoneal schwannoma mimicking an adnexal mass in pregnancy

A 36-year-old pregnant woman attended her first trimester scan and there was an incidental finding of a right-sided complex cystic adenexal mass. Further investigations including repeat pelvic ultrasound scans and MRI were performed due to its complex nature but were inconclusive. Multidisciplinary team review of images found the mass to be retroperitioneal, neurogenic in origin and involving the L5 vertebrae. The pregnancy continued to term and the baby was delivered at 39 weeks gestation by elective caesarean section due to the mass being likely to obstruct progress in labour. Postnatal biopsy confirmed a schwannoma. Plans were made for resection however as the woman was asymptomatic she declined surgery in favour of completing her family. She conceived again 2 years later and a second pregnancy was managed in the same way. The size of the schwannoma remained stable throughout this period.