Abstract
Common causes of unilateral breast uptake of Tc-99m pertechnetate are predominant breast-feeding on one side, mastitis, and breast cancer. Uptake of Tc-99m pertechnetate in the epithelial cells of the breast, like that of iodide, depends on the transmembrane sodium/iodide symporter (NIS), the expression of which is known to be greatly enhanced during lactation and in breast cancer. The authors present an interesting case of predominant left breast uptake of Tc-99m pertechnetate detected incidentally during thyroid scintigraphy, for the evaluation of a nodule in the left lobe of thyroid.