A Case of Placental Site Trophoblastic Tumour That Mimicked Missed Miscarriage

Background and Clinical Significance: Placental site trophoblastic tumour (PSTT) is a malignant tumour of the implantation site intermediate trophoblasts. It has historically been described using terms such as atypical chorioepithelioma, atypical choriocarcinoma, syncytioma, and chorioepitheliosis. It belongs to one of the heterogeneous spectrums of gestational trophoblastic disease. It accounts for about 0.25 to 5% of all gestational trophoblastic neoplasia. The typical clinical presentation is alternating menorrhagia and amenorrhea, mildly elevated β-hCG, and radiological findings of a uterine mass. Case Presentation: A 32-year-old woman presented with a history of intermittent menorrhagia and amenorrhea, with a persistent mildly raised β-hCG level. Ultrasonography showed a hypoechoic lesion on the right side of the posterior wall of the uterus. She was diagnosed with a missed miscarriage, and an evacuation of the products of conception was performed. Histologically, the tissue fragments comprised cords and sheets of atypical intermediate trophoblast cells, with characteristic features of myometrial smooth muscle infiltration, vascular invasion, and vascular wall replaced by the neoplastic cells. Immunohistochemically, these cells are positive for β-hCG and GATA3, while negative for P63. Conclusions: PSTT is a rare form of gestational trophoblastic neoplasia. Early recognition of PSTT is essential because its clinical presentation may mimic benign pregnancy-related conditions, and diagnosis relies heavily on histopathological and immunohistochemical evaluation.