Unusual 131I Uptake in a Benign Mucinous Cystadenoma of the Ovary in a Patient With Papillary Thyroid Cancer

We present a huge benign mucinous cystadenoma of the ovary, incidentally discovered by I-131 whole-body scan and I-131-SPECT/CT as a false-positive I-131 uptake in a patient with papillary thyroid cancer. I-131 whole-body scan and I-131-SPECT/CT performed after I-131 administration revealed an abnormal focus of I-131 uptake in a huge mass of the pelvis. The pelvic mass was histologically confirmed to be a benign mucinous cystadenoma of ovary. The case is a classic example of false-positive findings on I-131 whole-body scan for differentiated thyroid cancer.