823 The Dilemma of Managing the Thyroid Gland After Incidental Diagnosis of Malignant Struma Ovarii, Is Radical Thyroidectomy and Radioactive Iodine Necessary? a Case Report and Literature Review

Abstract

Abstract Background Struma Ovarii is a unique type of ovarian teratoma which occurs when thyroid tissue constitutes 50% or more of the tumour. Most of these tumors are benign, however malignant transformation happens in less than 3%. Thyroid carcinomas can occur as distal metastasis with malignant struma ovarii (MSO) however, their diagnosis and treatment remain debatable. Case We report on a case of a 48-year-old woman whose MSO was discovered accidentally during a clinical trial. An ultrasound (US) depicted a complex left adnexal mass, which an MRI subsequently confirmed. The mass measured 4.5cmx 2.5cmx 5.0cm, a strong Doppler blood flow, and nodularity were noted. Salpingo-oopherectomy, omentectomy, appendicectomy, and left pelvic and para-aortic lymph node dissection were performed. The postoperative histopathological assessment of the tumour confirmed the diagnosis of MSO. The patient was then reviewed by a head and neck multi-disciplinary meeting. A 6mm thyroid nodule was located on the left lobe, and the cytology was reported as negative on fine needle aspiration (FNA). Nonetheless, the patient was treated with a radical thyroidectomy and radioactive iodine. Post-operative histopathology reported thyroid carcinoma, despite the negative cytology on FNA. No recurrence was noted. Conclusions This case highlights the importance of radical treatment of the thyroid in patients with MSO. Accurate preoperative diagnosis of thyroid carcinoma secondary to MSO is difficult, since pathological diagnosis is the gold standard. Our case showed that a radical treatment of thyroid with surgery and radioactive iodine minimises the risk of local and distal recurrences.