There are various possible causes of false-positivity on I-131 WBS after thyroidectomy for DTC: functional sodium iodide symporter expression in normal tissue, benign and malignant tumor, metabolism of radioiodinated hormone, retention of radioiodinated body fluids associated structural change, retention and uptake of radioiodine in inflamed tissue, contamination by physiologic radioiodine uptake [11, 12]. The gene discussed is SLC5A5; the disease is cancer.