Abstract: The sodium iodide symporter（NIS） is a transmembrane glycoprotein that mediates active iodide uptake into thyroid follicular cells. NISmediated iodide uptake in thyroid cells is the basis for treatment of differentiated thyroid carcinomas and their metastases. Furthermore， NIS is expressed in many human breast tumors， suggesting that NISmediated radionuclide uptake may be used for the targeted therapy of breast cancer. However， functional cell surface NIS expression is often low in breast cancer， making it important to uncover signaling pathways that modulate NIS expression at multiple levels， from gene transcription to posttranslational processing and cell surface trafficking. In this review， we summarized the research progress of the presence， relevance and regulation of NIS in breast cancer. The clinical significance of NIS in breast cancer radioiodine therapy will also be discussed.