Thyroid gland ectopia to the ovary resulting in papillary thyroid cancer with carcinomatosis

Thyroid gland ectopia is a rare condition occurring as a developmental anomaly during the embryonic period, when the thyroid primordium migrates. The prevalence of thyroid gland ectopia is 1 per 100 000–300 000 healthy individuals. Struma ovarii is a variant of thyroid gland ectopia, defined by the presence of thyroid tissue in the ovary. Cases of struma ovarii are very rare, and in the pediatric population they are even more rare than in adults. Only a few cases of struma ovarii in patients under 18 years have been described in the literature. Here, we present a clinical case of papillary thyroid cancer in ectopic thyroid tissue in a 13-year-old girl. The patient's parents gave their consent to the use of their child's data, including photographs, for research purposes and in publications. Surgery remains the main treatment option for all histological subtypes of thyroid cancer, however patients with distant metastasis are treated with radioactive iodine therapy. In this case, as adjuvant therapy, the patient received a combination of thyroidectomy and radioactive iodine therapy due to the presence of implantation metastases. Malignant transformation of ectopic thyroid tissue is extremely rare, and it may be difficult for a clinician to determine the best treatment option due to the lack of uniform treatment guidelines for this disease. This case report describes the clinical course of struma ovarii as well as an option for surgical treatment and adjuvant therapy for this disease.