Tc-99(m)-MIBI scintimammography for the detection of breast malignancies: The contribution of the count ratio to specificity

We evaluated the efficacy of Tc-99(m)-sestamibi (MIBI) scintimammography fo r the detection of breast cancer in 332 patients. Two hundred and seven sca ns were confirmed by histological or cytological results; the other patient s were examined because they belonged to high-risk groups or had dense fibr oglandular breasts. Of 207 patients with histological confirmation, 112 pos itive studies were obtained: 86 true-positive and 26 false-positive. Scinti mammography was negative in 95 patients: 88 true-negative and seven false-n egative. Six of seven false-negative results were obtained in patients with impalpable tumours. The sensitivity, specificity, positive and negative pr edictive values were 92.5%, 77.2%, 76.8% and 92.6% respectively The overall accuracy was 84.1%. To identify false-positive results, the count ratio of the target lesion to the contralateral normal area on 38 true-positive sca ns and in 26 false-positive examinations was calculated from the region of interest drawn on the Tc-99(m)-MIBI scan (L/N ratio). A significantly highe r ratio was found for the true-positive scans (1.583 +/- 0.501 vs 1.246 +/- 0.213; P = 0.0002). In conclusion, Tc-99(m)-MIBI scintimammography is a se nsitive and accurate method for the detection of breast malignancies. ((C) 1999 Lippincott Williams & Wilkins).