A failure in detecting NIS expressing local recurrences or metastases of DTC might result both in a missed opportunity for localized therapy and an erroneously assumed TENIS (thyroglobulin elevated negative iodine scintigraphy) syndrome found in cases of recurrent DTC with dedifferentiation of tumor cells that decrease NIS expression but increases 18F FDG metabolism, in turn. The gene discussed is SLC5A5; the disease is neoplasm.