SUN-335 Management of Monodermal Teratoma Struma Ovarii with Non-Invasive Follicular Thyroid Neoplasm

Abstract Disclosure: I. Kozak: None. Z. Zavgorodneva: None. K. Naher: None. Introduction:Ovarian teratomas are the most common type of germ cell tumors. Struma ovarii, is a rare ovarian tumor, often goes undiagnosed until it manifests clinically with nonspecific symptoms and is diagnosed postoperatively by pathology results. Despite low metastatic progression there are no clear guidelines in management given rarity of the tumor. Surgical treatment including unilateral salpingo-oophorectomy, or total abdominal hysterectomy with bilateral salpingo-oophorectomy, in addition to total thyroidectomy and radioactive iodine (RAI) ablation are the commonly used options. Case report: A 62-year-old female was referred to the Endocrinology clinic for evaluation of a multinodular goiter (MNG) of the thyroid gland. Her past medical history was significant for struma ovarii, which was diagnosed during a bilateral salpingo-oophorectomy (BSO) performed six months prior for a complex ovarian cyst. The surgery was prolonged due to significant adhesions and was complicated by intestinal perforation, requiring reconstructive surgery. Immunohistochemical staining of the left ovary was consistent with monodermal teratoma/struma ovarii, with features of a non-invasive follicular thyroid neoplasm with papillary-like nuclear features (2.5 cm), confirming the diagnosis. The postoperative period was complicated by a pulmonary embolism (PE). A follow-up CTA, conducted three months after initiating anticoagulation, showed resolution of the PE and revealed a heterogeneously enlarged multinodular thyroid with substernal extension into the upper mediastinum. A dominant nodule in the left thyroid lobe, measuring greater than 15 mm, was identified. Thyroid ultrasound confirmed the presence of a multinodular goiter (MNG), including a nodule in the left lobe measuring 1.64 cm, classified as TIRADS 3. Fine needle aspiration (FNA) of this nodule was performed, resulting in a Bethesda category II, suggesting benign features. Despite the benign FNA result, the patient was referred for thyroidectomy to manage the multinodular goiter (MNG) and ensure ongoing surveillance for potential recurrence of struma ovarii. Discussion:In some cases, where clear signs of malignant struma ovarii are absent but atypical features are present, established guidelines may not offer definitive guidance. In such instances, management should be individualized. We suggest that thyroidectomy be considered, particularly when concurrent thyroid pathology is identified, with repeated biopsy may be necessary for ongoing evaluation and diagnosis. Moreover, in non-invasive follicular thyroid neoplasm of struma ovarii, measuring thyroglobulin levels may be a valuable marker, potentially indicating a relapse of the disease and guiding the decision to consider radiation therapy. This could represent another indication for thyroidectomy. Presentation: Sunday, July 13, 2025