Long-term survival in metastatic malignant struma ovarii treated with oral chemotherapy: A case report

Malignant struma ovarii is a rare type of ovarian tumor. Metastasis from malignant struma ovarii is rare and has only been documented in 5–6% of cases. The natural history and optimal treatment strategy for malignant struma ovarii remains controversial due to its rarity. The current report presents the case of a 45-year-old female who presented with a tumor of the rib bone. Following resection, the postoperative diagnosis was a metastasizing thyroid carcinoma. No abnormality was detected in the thyroid gland, however, computed tomography revealed a tumor in the left ovary. The patient underwent a left salpingo-oophorectomy and a wedge resection of the right ovary. The postoperative diagnosis was determined as a mature cystic teratoma with malignant struma ovarii (thyroid type, follicular carcinoma) of the left ovary and mature cystic teratoma of the right ovary. Four years subsequent to the initial diagnosis, multiple lung metastases were detected. The following chemotherapies were administered sequentially and intermittently: Tegafur-uracil, paclitaxel/carboplatin and oral etoposide. During this period, the metastatic lesions extended into the bone and progressed slowly. The patient continues to survive with the disease and 24 years have passed since the initial diagnosis, 20 years following the diagnosis of multiple lung metastates. The present report describes a rare case of malignant struma ovarii in which surgical resection and pathological examination of a metastatic rib tumor resulted in the identification of the primary ovarian lesion. The clinical behavior of malignant struma ovarii does not necessarily indicate a histological malignancy, therefore, prediction of future metastasis is difficult and the optimal treatment strategy for malignant struma ovarii is controversial. The present case indicates that the long-term use of oral anticancer agents may facilitate the maintenance of tumor dormancy.