Background: Malignant struma ovarii is a rare malignant germ cell tumor of the ovary. Due to the rarity of this disease, treatment has not been uniform throughout the published literature.
Cases: We present three cases of malignant struma ovarii. Following primary surgery, all were subsequently treated with thyroidectomy and 131I ablation therapy, two patients as first line management, one following the occurrence of metastatic disease.
Conclusion: Histological diagnosis of malignant struma ovarii is similar to that of well differentiated thyroid carcinoma (WDTC). In line with the latest advice on treatment of WDTC, we believe that the best option for patients with malignant struma ovarii is surgical removal of the ovarian lesion followed by total thyroidectomy which allows the exclusion of primary thyroid carcinoma, and in addition, allows radioiodine (131I) ablation therapy for (micro) metastasis. After thyroidectomy, thyroglobulin can be used as a tumor marker for follow-up. Moreover, nuclear medicine imaging using radioiodine (123I) can be performed to demonstrate metastatic carcinoma. A multidisciplinary approach is essential.