Atypical placental site nodule detected via hysteroscopy – first case report from Brazil

Atypical placental site nodule (APSN) is a rare form of gestational trophoblastic disease (GTD) originating from the proliferation of intermediate trophoblasts, with uncertain clinical behavior. It is considered a potential precursor to rare forms of gestational trophoblastic neoplasia (GTN), such as placental site trophoblastic tumor (PSTT) and epithelioid trophoblastic tumor (ETT). This report describes the first Brazilian case of APSN diagnosed via hysteroscopy in a 43-year-old woman following miscarriage. Histopathological analysis revealed a circumscribed, hyalinized aggregate of intermediate trophoblasts with nuclear atypia, positive immunostaining for PLAP and p63, and a Ki-67 index > 5%. The patient declined hysterectomy, opting for conservative management with close monitoring. After 12 months of follow-up, no progression was observed. This case emphasizes the diagnostic challenges of APSN, given its subtle presentation and overlap with benign placental site nodules or even PSTT/ETT. Hysteroscopy proved valuable for both diagnosis and fertility-preserving management. Although hysterectomy remains the definitive treatment in many cases, individualized approaches balancing oncologic safety and reproductive goals are increasingly considered. Long-term clinical vigilance is essential, as APSN may precede aggressive GTN forms. Multicenter studies and registries are urgently needed to establish evidence-based guidelines for the diagnosis, treatment, and follow-up of this rare lesion, improving patient outcomes in these uncommon forms of GTD.