Abstract
BackgroundMalignant struma ovarii is an ovarian teratoma containing at least 50% thyroid tissue which has the potential to metastasize and produce thyroid hormone. Given its rarity, management strategies are not well-established. We report a case of metastatic malignant struma ovarii discovered during pregnancy with lessons for evaluation and management.Case presentationA 30-year-old woman who was two months pregnant was discovered to have struma ovarii with over half of the struma comprised of papillary thyroid cancer. Following tumor resection, delivery, and thyroidectomy, she underwent evaluation with stimulated thyroglobulin testing and diagnostic staging sodium iodide-131 scan (I-131), which revealed the presence of skeletal metastases. Following administration of 320 mCi I-131, post-therapy scan also showed miliary pulmonary metastases with improved ability to localize the bony and pulmonary metastases with concurrent SPECT/CT imaging. A second dosimetry-guided I-131 therapy resulted in complete resolution of pulmonary metastases; however, small foci of residual bone disease persisted. Post-therapy scans demonstrated additional findings not shown on diagnostic I-131 scans obtained prior to both her initial and second I-131 therapy.ConclusionsSPECT/CT provides accurate anatomic correlation and localization of metastatic foci and can serve as a baseline study to assess interval response to treatment. Post-therapy scans should always be obtained when I-131 treatment is administered, as additional findings may be revealed versus low dose I-131 activity diagnostic scans. This patient had a high metastatic burden that would not have been discovered in a timely fashion with the conservative approach advocated by others. Thyroidectomy followed by a diagnostic staging radioiodine scan and a stimulated thyroglobulin level should be considered in patients with malignant struma ovarii for guiding therapeutic I-131 administration as metastatic risk is difficult to predict based on histopathologic examination.
Highlights
ConclusionsSPECT/CT provides accurate anatomic correlation and localization of metastatic foci and can serve as a baseline study to assess interval response to treatment
Malignant struma ovarii is an ovarian teratoma containing at least 50% thyroid tissue which has the potential to metastasize and produce thyroid hormone
Thyroidectomy followed by a diagnostic staging radioiodine scan and a stimulated thyroglobulin level should be considered in patients with malignant struma ovarii for guiding therapeutic iodide-131 scan (I-131) administration as metastatic risk is difficult to predict based on histopathologic examination
Summary
This unusual case presents important considerations in the care of patients with malignant struma ovarii. Staging with a diagnostic whole body radioiodine scan and stimulated Tg level following thyroidectomy needs to be considered in all patients with intermediate and high-risk histopathology findings. The I-131 scan should include SPECT/CT imaging, which can demonstrate additional areas of metastases missed on planar imaging, allows for accurate anatomic correlation of metastatic lesions, and can impact treatment decisions [16]. When I-131 treatment is given, a post-therapy I-131 scan should always be obtained two-seven days after treatment to assess for additional findings as compared with the diagnostic I-131 scan [17]. The role of sex hormones and hCG in thyroid cancer arising from both struma ovarii and the thyroid gland should be explored further
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