Radiographic mammography (MM) is routinely used to diagnose breast cancer. MM has a number of well-known limitations, especially in cases of a dense or dysplastic breast. Scintimammography (SM) with Tc-99m MIBI has been successfully used as a useful complement to MM. The authors report a case of a 57-year-old woman with MM with tiny calcifications in the left breast, which were classified by the radiologist as probably benign lesions. SM with Tc-99m MIBI showed a focal area of increased uptake in the upper outer quadrant of the left breast. On the basis of SM results, an excisional biopsy was performed and pathologic examination revealed infiltrating ductal carcinoma.