Ganglioneuroblastoma is a variant of neuroblastoma tumours with mature ganglion cell differentiation which occurs commonly in cervical, mediastinal and retroperitoneal locations. Approximately 90% of ganglioneuroblastomas are seen in children younger than five years old. There are 50 adult cases of ganglioneuroblastomas reported to date. Our patient is the 51st case and she is the first to be diagnosed in pregnancy. Our patient’s tumour site was the thoraco-abdominal retroperitoneal space adjacent to her kidney. This tumour is generally diagnosed incidentally or by compression presentations, i.e. pain or neurological symptoms. Our patient’s ultrasound scan appearances triggered suspicion of an atypical mass after presenting with loin pain. Caesarean section with tumour removal in the same session is preferred if tumour is small and localized. However in this case, there was uncertainty regarding the extent of the tumour. Therefore, the patient underwent thoracotomy after delivery to excise the thoraco-abdominal tumour, which extended from the level of the T9 to L2 vertebrae. [ABSTRACT FROM AUTHOR]