Missed Initial Diagnosis Of Malignant Struma Ovarii Containing Follicular Thyroid Carcinoma: Metastatic Pulmonary Recurrence 17 Yr After Ovariectomy

Distant metastasis of rare malignant struma ovarii (MSO) has been reported for cases associated with papillary thyroid cancer but few with follicular thyroid cancer. A 38-yr-old woman with struma ovarii that was initially diagnosed as benign presented with pulmonary metastasis and coughing 17 yr later. The lungs lesions were confirmed to be follicular thyroid cancer by biopsy. Rereview of the initial surgical ovary specimens confirmed the condition to be MSO with follicular thyroid cancer. The patient was treated with total thyroidectomy, which showed no thyroid malignancy, followed by I-131 (iodine-131) treatments. Dramatic reduction was observed in both the stimulated thyroglobulin level and the size of the pulmonary metastases over 1 yr. During the following 3-yr follow-up, the patient remained clinically well, with undetectable thyroglobulin (<1 ng/mL) and small stable pulmonary lesions. This is an exceedingly rare case of MSO with follicular thyroid cancer metastasized to the lungs presenting with a late onset but a fortunate excellent response to multidiscipline treatments. It is advisable that struma ovarii be carefully examined to avoid missing malignancy and patients be clinically followed up even with a benign initial diagnosis.