A 44-year-old woman had a history of papillary thyroid carcinoma and underwent total thyroidectomy and I ablation therapy. During the follow-up, 2-mCi I cancer workup showed an unusual shape of uptake in the pelvic region. Hybrid SPECT/CT revealed uptake posterior to the uterus, where sonography showed an 85.4-mm right ovarian endometrioma just corresponding to the location. Laparoscopic salpingo-oophorectomy showed right ovarian endometrioma (7 cm) and left ovarian cyst (4 cm). Pathologic findings showed bilateral endometriosis. After that survey, follow-up I cancer workup showed left supraclavicular, pretracheal, and right hilar metastatic lymphadenopathy with pulmonary metastasis, but no pelvic uptake was noted.