Papillary Thyroid Carcinoma Arising Within a Mature Ovarian Cystic Teratoma: A Case Report

<b>Introduction:</b> Mature cystic teratoma is a common benign ovarian germ cell tumor containing well-differentiated cells from three germ layers. Malignant transformation within these teratomas, such as papillary thyroid carcinoma, is extremely rare. <b>Case Report:</b> A 62-year-old asymptomatic woman was found to have a 5 cm hyperechoic lesion with an internal cystic component in her left ovary, suspected to be a mature teratoma. A total hysterectomy with bilateral salpingo-oophorectomy was performed, removing an unruptured, thin-walled ovarian tumor. Gross pathology revealed a uni-loculated solid-cystic lesion with smooth serosa, a homogenous tan solid part containing soft tan hair, and no papillary projections, adhesions, or ascites. Pathology identified a 2 cm papillary thyroid carcinoma (classic subtype) arising in a 4.7 cm mature teratoma, without lymphovascular invasion or ovarian surface involvement. Thyroid ultrasound, thyroid function tests, and PET imaging showed no abnormalities or metastasis. The role for total thyroidectomy and radioactive iodine ablation was discussed. After reviewing the pathology and confirming the absence of aggressive tumor behavior, shared decision-making led to opting against further treatment. Three years postoperatively, there was no recurrence or metastasis. <b>Conclusions:</b> This case describes the rare occurrence of papillary thyroid carcinoma within a mature ovarian teratoma. Currently, there is a lack of consensus on postoperative management. In selected cases with no evidence of metastasis or aggressive features, conservative management may be a reasonable option after thorough evaluation.