Benign Struma Ovarii in a Patient With Invasive Papillary Thyroid Cancer: Detection with I-131 SPECT-CT

A 78-year-old woman was referred for I-131 therapy following total thyroidectomy for invasive papillary thyroid cancer. The thyroglobulin titer was markedly elevated following thyroxine withdrawal, and she was given 5,550 MBq (150 mCi) of I-131 following additional pretreatment with rTSH (Thyrogen). A posttherapy scan showed intense, focal activity in the pelvis, which localized to the right ovary on SPECT-CT fusion examination. Contrast CT confirmed a cystic right ovarian tumor and she underwent laparoscopic oophorectomy, which revealed a benign follicular thyroid adenoma (struma ovarii). At 6-month follow-up, a whole body iodine scan was normal, and the TSH-stimulated thyroglobulin was undetectable.