Retrospective Multicenter Analysis of Malignant Struma Ovarii: Clinical Characteristics, Management, and Outcomes

<b>Background/objectives:</b> The study aimed to present cases of malignant struma ovarii from seven centers in Türkiye and evaluate them within the context of the existing literature. <b>Methods:</b> We retrospectively analyzed clinical data from 17 patients treated at seven centers, focusing on clinical features, surgical management, pathology, thyroid function, adjuvant treatment, and outcomes. Additionally, a literature review including eight studies with 178 patients was conducted. <b>Results:</b> The mean age of patients was 44.7 years, with a mean tumor size of 9.2 cm. Elevated Ca 125 was found in 33.3% of patients, while thyroid function abnormalities and hyperthyroidism signs were rare. Pelvic pain and menstrual irregularities were common presenting symptoms. A total of 16 patients (94.1%) had unilateral tumors. Total abdominal hysterectomy with bilateral salpingo-oophorectomy and unilateral salpingo-oophorectomy were the most frequent surgical approaches. Histopathology predominantly showed classical papillary thyroid carcinoma (13 patients, 76%). All patients were FIGO stage I, with no metastasis. Thyroidectomy was performed in seven patients, identifying two concurrent thyroid cancers. Four patients received adjuvant radioactive iodine therapy. During a median follow-up of 43 months, no deaths and one recurrence were observed. The literature review showed a diagnosis age ranging 43-53 years and papillary thyroid carcinoma as the most common subtype. Thyroidectomy and RAI treatment were selectively applied. Among the reported studies, recurrence occurred in 7 of 76 patients (9.2%), while 5-year disease-free and overall survival rates exceeded 94% and 100%, respectively. BRAF mutations were uncommon. <b>Conclusions:</b> Malignant struma ovarii is a rare tumor with a favorable prognosis when diagnosed early and managed appropriately.