Papillary Thyroid Carcinoma Arising in Struma Ovarii With Subsequent Thyroid Microcarcinoma: A Case Report and Review of the Literature.

Struma ovarii is a rare form of monodermal ovarian teratoma composed predominantly of thyroid tissue. In exceptional cases, malignant transformation occurs, most commonly as papillary thyroid carcinoma. The subsequent appearance of thyroid malignancy in the cervical gland presents a diagnostic and therapeutic dilemma, particularly in differentiating between metastatic disease and metachronous or synchronous primary tumors. We report the case of a 43-year-old female patient with hypothyroidism who underwent laparoscopic adnexectomy for a symptomatic ovarian mass. Histopathological examination revealed a mature cystic teratoma with a focus of classic papillary thyroid carcinoma, without evidence of capsular or vascular invasion. Three years later, thyroid ultrasound identified a subcentimeter nodule classified as TIRADS 5, and fine-needle aspiration confirmed Bethesda VI cytology. Total thyroidectomy revealed a 4 mm unifocal classic papillary carcinoma, with no capsular or lymphovascular invasion and negative lymph nodes. Following thyroidectomy, no adjuvant radioactive iodine therapy was administered, and the patient remains disease-free after three years of surveillance. This case highlights the clinical challenge in distinguishing metachronous primary thyroid carcinoma from metastatic disease in patients with a prior diagnosis of malignant struma ovarii. Furthermore, it raises important considerations regarding the need for thyroidectomy and radioiodine therapy in such patients, especially when subcentimeter thyroid nodules are identified. In the absence of consensus guidelines, therapeutic decisions must be individualized, guided by tumor behavior, patient risk factors, and the available evidence. Reporting such cases is essential to inform clinical practice and refine follow-up strategies in this rare clinical scenario.