Incidental Detection of Struma Ovarii on the Whole Body Scan in a Differentiated Thyroid Cancer Patient

ABSTRACT

Post-therapeutic whole body scan (RxWBS) after radioactive iodine (RAI) remnant ablation (RRA) is useful for detect recurrent or metastatic foci of differentiated thyroid carcinoma (DTC) after total thyroidectomy. However, there is rare possibility of false positive iodine uptake in WBS. Here, we report a case of a 72-year-old woman, who underwent RRA after total thyroidectomy due to follicular variant papillary thyroid carcinoma. There is an abnormal iodine uptake in RxWBS in pelvic cavity. Additional single photon emission computed tomography (SPECT)-computed tomography (CT) imaging showed an intensive I-131 avid mass in left ovary. There was a multiple calcified mass in left ovary and enhancing wall thickening in left ureter with hydronephrosis in contrast enhanced CT. She underwent hysterectomy, oophorectomy, left ureterectomy and nephrectomy and diagnosed as mature cystic teratoma with thyroid tissues and ureter cancer. Struma ovarii should be considered if there was abnormal RAI uptake in pelvic cavity. I-131 SPECT-CT is useful for differential diagnosis of abnormal iodine uptakes in WBS.