P-80 A rare case of papillary thyroid carcinoma within a mature cystic ovarian teratoma

Abstract

Abstract Introduction Mature teratoma is the most common ovarian germ cell neoplasm. Teratomas can contain various tissue groups, such as skin, hair, and thyroid tissue. Teratomas in which more than 50% of the tumor tissue is composed of thyroid tissue are defined as Struma Ovarii. Malignant transformation of Struma Ovarii has been reported at a rate of 0.5-5%, most commonly presenting as thyroid papillary and follicular carcinomas. Metastasis is observed in 5% of malignant cases. Clinical Case A 45-year-old female with a history of Hashimoto's thyroiditis presented in July 2022 with complaints of abdominal pain. Abdominal contrast-enhanced tomography revealed a hypo dense lesion 5 cm in diameter the right adnexal region, and in the magnetic resonance images 5 cm mass was observed in the right adnexal area. Serum Ca-125 level was 212 U/mL (0-35) at admission. Due to high suspicion of malignancy ovarian cystectomy has been performed. Pathology of specimen revealed a 0.5 cm thyroid papillary carcinoma with follicular variant in infiltrative features but no lymphovascular invasion. Subsequently, the patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy due to the unverifiable risk of malignancy. Pathological examination showed no malignancy. The patient presented to our clinic in June 2023, neck ultrasound revealed a 13×12 mm heterogeneous hypoechoic thyroid nodule with thick and thin septations and occasional internal vascularity in the left thyroid lobe. Fine-needle aspiration biopsy of the thyroid was performed, and cytology results were reported as benign. The serum thyroglobulin level was found to be 83.7 ng/mL. In terms of the treatment plan, BRAF and K-RAS gene analysis was planned based on the pathology preparations. The patient will be evaluated for total thyroidectomy/radioactive iodine ablation/no treatment based on the results. Follow-up is ongoing, and test results are awaited. Conclusion Malignant transformation of mature teratoma is rare and thyroid papillary carcinoma being the most frequently seen malignancy. There is no consensus on treatment and follow-up, but it is recommended to classify patients based on their risks and consider options such as total thyroidectomy/radioactive iodine ablation/no treatment for follow-up. Literature suggests the need for guidelines and treatment algorithms for the management of malignant struma ovarii. Some authors recommend whole-body iodine scanning in determining risk and follow-up, asserting that iodine-based treatment and follow-up methods would be meaningless without thyroidectomy. There is also an approach advocating for only salpingo-oophorectomy in low-risk patients and subsequent follow-up. Thus, a consensus on guidelines and treatment algorithms for malignant struma ovarii is needed.