Unilateral Tc-99m pertechnetate breast uptake: is it always benign?

Although the thyroid gland is the principal organ with the ability to concentrate iodide and take up Tc-99m pertechnetate, other tissues such as choroid plexus, salivary glands, mucoid cells of stomach, and lactating breast tissue also possess this property. The lactating mammary gland can concentrate iodide, which mediated by sodium/iodine symporter (NIS) is actively transported and secreted in the milk, to supply iodide to the newborn for the biosynthesis of thyroid hormones. The authors present an uncommon case of unilateral Tc-99m breast uptake in a breast-feeding woman.