SMARCA4-Deficient Undifferentiated Uterine Sarcoma Presenting as Nonpuerperal Uterine Inversion in a Morbidly Obese Woman: A Case Report

SMARCA4-deficient undifferentiated uterine sarcoma (SDUS), which mainly occurs in young patients, is a recently recognized, highly aggressive malignancy with an extremely poor prognosis.Nonpuerperal uterine inversion (NPUI) is a rare condition most commonly associated with uterine tumors.Here, we report a case of NPUI caused by SDUS.A 25-year-old woman (body mass index, 48 kg/m²) presented with irregular vaginal bleeding.Pelvic examination revealed a vaginal mass extending from the cervix to the introitus region.Pelvic magnetic resonance imaging revealed uterine inversion secondary to an endometrial mass.Tumor scrape cytology showed no malignant cells.Tumor resection and uterine repositioning were performed to preserve fertility.Histopathological examination findings revealed an undifferentiated malignant tumor, while immunohistochemical analysis confirmed a diagnosis of SDUS.Computed tomography revealed para-aortic lymph node enlargement, suggesting metastatic involvement.The patient subsequently underwent total abdominal hysterectomy, bilateral salpingo-oophorectomy, and excision of an enlarged para-aortic lymph node.Based on these pathological findings, the patient was diagnosed with SDUS with para-aortic lymph node metastasis (FIGO stage IIIC) and received adjuvant chemotherapy with doxorubicin.Following completion of six chemotherapy cycles, our patient remained disease-free at 12 months postoperatively.This is the first reported case of SDUS presenting as NPUI in a patient with severe obesity.Optimal management of SDUS has not yet been established, but complete surgical resection may play an important role in disease control.