Introduction: Diagnostic and post-therapy radioiodine whole body scan (WBS) is used in the follow-up of differentiated thyroid carcinoma (DTC) for the detection of local recurrence or remote metastasis. We report a case of false-positive uptake of radioiodine WBS.
Case report: A 37-year-old female patient underwent subtotal thyroidectomy for multinodular goitre and histology revealed multifocal papillary thyroid carcinoma, of follicular type with three foci of major diameter 1.35 mm. Post-operative radioiodine uptake of 24 h was 2.7% and thyroglobulin (Tg) levels were 35 ng/ml. Neck ultrasound was negative for pathologic lymph nodes and chest X-ray was unremarkable. An ablation dose of 70 mCi radioiodine was administered and the post-therapy WBS demonstrated multiple thyroid remnants on the anterior cervical region, increased uptake on the anterior upper mediastinum and a third large focus in the middle of the chest most evident on the posterior views suggesting vertebral metastatic involvement. Chest CT scan, cervical and mediastinal MRI were negative. In the 99Tc-bone scan a small focus of increased uptake was observed at the 8th thoracic vertebrae with no other pathologic findings of the skeleton. MRI of the spine showed a high intensity pathologic signal in the 8th thoracic vertebrae with a major frontal diameter of 14.6 mm, which is most likely attributed to an atypical hemangioma and not to metastatic disease, in line with the rather mild elevation of Tg levels. Bone metastases in DTC are known to cause higher Tg concentrations, usually >100 ng/ml.
Discussion: Vertebral hemangiomas are common and radioiodine uptake by a vertebral hemangioma in a patient with DTC has been reported in the literature in very few cases. These false positive results may mislead the physician to the presence of distant metastasis and erroneously change the stage of the disease and the therapeutic approach.
16 - 20 May 2015
European Society of Endocrinology