Rare Clinical Entity: Metastatic malignant struma ovarii diagnosed during pregnancy – Lessons for management

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.

FIGO Stage IV and Age Over 55 Years as Prognostic Predicators in Patients With Metastatic Malignant Struma Ovarii

“…It was found that 25.3% (20/79) of patients were younger than 35 years at the time of diagnosis, which is in the time period of child-bearing age. There is little literature on pregnancy or fertility preservation in MSO that has been published ( 35 – 39 ). Even though it is extremely rare, complications in fertility preservation and management of pregnancy in metastatic MSO cannot be neglected.…”

“…Ihalagama et al reported an uneventful pregnancy after USO, a total thyroidectomy, and RAI in a patient with non-metastatic MSO ( 35 ). Larger et al ( 39 ) and Tokuda et al ( 38 ) presented disease management in cases of accidental diagnosed with metastatic MSO after conception. The former case was treated with USO and RAI, while the latter was treated with a simple metastasis resection, but this case lacked follow-up information.…”

Retrospective Diagnosis of Malignant Struma Ovarii After Discovery of Pulmonary Metastasis

“…Cancer antigen 125 is a common tumor marker for malignant struma ovarii but is of very low diagnostic value due to its nonspecificity. 10 A broad panel of immunohistochemical stains, including paired-box gene 8, thyroid transcription factor 1, and TG, can be helpful to differentiate malignant struma ovarii from other ovarian malignancies, but it has not been reported if they can help to differentiate benign vs malignant struma ovarii. 11 It remains to be seen if markers found to be useful in thyroid malignancies, such as HBME-1, specific cytokeratins (eg, cytokeratin 19), and RET, might be helpful in the diagnosis of malignant struma ovarii.…”

“…In our case, the histopathological findings of metastatic tissue very close in appearance to normal thyroid tissue and I-131 uptake within these lesions argue that the tumor remained differentiated, maintaining its capacity to concentrate I-131. 10 , 15 The presence of thyroid microcarcinoma also raises the possibility of metastasis from primary thyroid malignancy; however, the thyroid carcinoma was 3 mm in size and had clear margins with no evidence of lymphovascular invasion, making metastasis from primary thyroid cancer less likely. Moreover, 2 of 3 pathologists agreed that the lung lesions were consistent with metastatic follicular carcinoma in the context of the diagnosis of struma ovarii, with follicular lesions similar in appearance to the lung.…”

Struma ovarii metast�sico, reporte de un caso

“…No existe un consenso sobre el tratamiento correcto de esta patología debido a la rareza del tumor. Existen informes que han propuesto una estadificación quirúrgica completa para el cáncer de ovario, algunos otros indican que una tiroidectomía total y iodo radiactivo pueden ayudar a la eliminación del tejido tiroideo residual después de la extirpación quirúrgica del tumor primario, así como en casos en que el tumor mida más de 2 cm, presente extensión extraovárica, metástasis a distancia, recurrencia o cáncer de tiroides primario concomitante 1,4,6,7,18,19 .…”