Case Report: Benign struma ovarii with pseudo-Meigs syndrome and advanced pelvic organ prolapse successfully managed by combined surgery

Introduction and importance Struma ovarii is a rare monodermal teratoma composed predominantly of mature thyroid tissue. Benign struma ovarii may be associated with pseudo-Meigs syndrome, characterized by ascites, pleural effusion, and elevated serum CA125 levels, thereby closely mimic advanced ovarian malignancy. Although these manifestations have been described previously, the coexistence of benign struma ovarii and advanced pelvic organ prolapse, as well as the feasibility of simultaneous surgical management, presents a clinically challenging scenario. Here, we report a case of benign struma ovarii associated with massive ascites, pleural effusion, markedly elevated CA125 levels, and severe uterine and vaginal prolapse, with emphasis on the diagnostic challenges and combined surgical management. Case presentation A 70-year-old postmenopausal woman presented with progressive abdominal distension and a protruding vaginal mass. Eleven months before admission, she developed abdominal distension and vaginal protrusion. Seven months before admission, ultrasonography at another hospital revealed a large pelvic cystic mass accompanied by massive ascites, raising suspicion of ovarian malignancy. Surgical treatment was recommended; however, given the patient's advanced age, her family initially opted for conservative treatment with oral Chinese herbal medicine. Her abdominal distension and vaginal protrusion subsequently worsened. Repeated paracentesis, protein supplementation, and diuretic therapy failed to provide sustained improvement. Biopsy of the ovarian mass and multiple cytological examinations of ascitic fluid using liquid-based cytology revealed no evidence of malignancy or atypical cells. Exploratory laparotomy was ultimately performed. Intraoperative frozen-section examination suggested a benign ovarian tumor, most consistent with a mature cystic teratoma. Total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, appendectomy, and posterior vaginal wall repair were performed during the same operation. Final histopathological examination confirmed struma ovarii. Three months after surgery, the patient's ascites and pleural effusion completely resolved, and her serum CA125 level returned to normal. No recurrence of ascites, pleural effusion, or prolapse-related symptoms was observed during 5 years of postoperative follow-up. Clinical discussion This case demonstrates the diagnostic complexity of benign struma ovarii associated with pseudo-Meigs syndrome and advanced pelvic organ prolapse. Massive ascites, pleural effusion, and markedly elevated CA125 levels may strongly suggest ovarian malignancy but are not specific for malignant disease. Therefore, imaging findings, tumor markers, cytological and pathological results, and intraoperative findings should be integrated to establish the diagnosis. In addition, the coexistence of a large pelvic mass, massive ascites, and advanced pelvic organ prolapse may substantially complicate surgical decision-making. In appropriately selected patients, simultaneous resection of the ovarian tumor and surgical correction of pelvic organ prolapse may be feasible, providing definitive treatment for both conditions in a single operative session. Conclusion Benign struma ovarii with pseudo-Meigs syndrome can closely mimic advanced ovarian malignancy, while its coexistence with advanced pelvic organ prolapse presents additional diagnostic and surgical challenges. A multidisciplinary and individualized approach may facilitate accurate diagnosis and surgical planning. When clinically appropriate, combined surgical management of the ovarian tumor and pelvic organ prolapse may be a feasible treatment strategy, as demonstrated by the favorable long-term outcome in this case.