Tc-99m Sestamibi Scintimammography for the Evaluation of Breast Masses in Patients with Radiographically Dense Breasts.

The objective of this study was to evaluate the usefulness of technetium-99m sestamibi (MIBI) scintimammography for the diagnosis of breast cancer in patients with palpable breast masses that cannot be adequately evaluated by mammography due to the presence of radiographically dense breasts. At 5 minutes after intravenous injection of MIBI, scintimammograms were obtained in 80 patients who had grade 3 or 4 glandular density on mammograms and a palpable breast mass. Excisional biopsy or FNA biopsy was obtained in 68 lesions in 67 patients. Scintimammography (22 true positive, 4 false positive, 41 true negative, 1 false negative) resulted in a sensitivity of 95.6%, specificity 91.1%, positive predictive value 84.6%, and negative predictive value 97.6%. Mammography (19 true positive, 21 false positive, 24 true negative, 4 false negative) resulted in a sensitivity of 73.9%, specificity 53.3%, positive predictive value 44.7%, and negative predictive value 80%. MIBI scintimammography has a higher sensitivity and specificity than mammography in patients with radiographically dense breasts. It is useful as an adjunct to mammography in those patients with radiographically dense breasts for the characterization of palpable masses. Although sensitivity of mammography in this cohort was high, its specificity was significantly lower than scintimammography. If validated in prospective studies it could provide a safe way of avoiding a breast biopsy in patients with benign findings on clinical exam, mammography, and needle aspiration cytology.