Nuclear scintigraphy is functional imaging and can be combined with anatomical imaging to improve diagnostic yield. Detection of parathyroid lesion by technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) can facilitate an appropriate operative approach in a patients with primary hyperparathyroidism. Tc-99m MIBI is concentrated in highly cellular or metabolically active tissues, which have abundant mitochondria. False-positive scintigraphic findings could be from head-and-neck carcinomas, thyroid neoplasm, and multinodular goiter. In addition, multiple organs outside of the neck region, such as lung and breast, can take up the Tc-99m MIBI. Herein, we report the occurrence of abnormal focal uptake in the breast region during the preoperative localization of parathyroid adenoma and later discovered breast carcinoma.