Concurrent Intrathyroidal Follicular Variant of Papillary Thyroid Carcinoma with Malignant Struma Ovarii Presenting 12 Years After Initial Diagnosis.

Malignancy in struma ovarii is rare and observed in only 5%-10% of patients. Here, we present a patient with malignant struma ovarii and coexisting intrathyroidal papillary thyroid carcinoma, with recurrence (large pouch-of-Douglas mass) and metastases (bilateral pulmonary and iliac nodal metastases) presenting 12 y after surgery. The notable features in this case were a concurrent intrathyroidal follicular variant of papillary carcinoma; the highly functioning nature of the malignant lesions, characterized by a low level of thyroid-stimulating hormone even without thyroxine suppression; and the low-grade ¹⁸F-FDG avidity of these lesions, consistent with their well-differentiated nature. With the adoption of a multimodality approach (surgery, radioiodine scintigraphic evaluation, and multiple radioiodine therapies), the patient showed a progressive decrease in the functionality of the disease, prolonged progression-free survival, and a good quality of life with symptom-free status at 5 y.