A prospective study of 77 breast cancer patients found that positron emission mammography (PEM) showed near-perfect agreement with surgical pathology for tumor multiplicity assessment and substantial agreement for tumor size measurements. PEM outperformed sono-mammography in the same evaluation. The dataset suggests PEM could improve preoperative mapping in settings where conventional imaging struggles to characterize extent of disease. The study framed performance against the reference standard of surgical pathology, which remains the most clinically definitive comparator. While the work supports PEM’s technical potential, it is still limited by sample size and study design; further multi-center validation would be needed before broad adoption.