【Abstract】Objective To assess the value of 99Tcm-tetrofosmin imaging in discriminating malignant mass from benign breast mass.Methods From June 2000 to January 2002, 104 patients with breast mass detected by clinical examination were included. After 740 MBq 99Tcm-tetrofosmin was injected intravenously in the contralateral arm to the breast lesion, the front and the lateral images were collected in 5 min, 10 min and 20 min respectively. 99Tcm-tetrofosmin imaging localized in breast was defined as the positive sign of affinitive tumor. All patients underwent operation within one week. Using histological assessment as a golden standard, the sensitivity, specificity, positive and negative predictive value for 99Tcm-tetrofosmin SPECT of the breast were calculated respectively. Results The sensitivity of 99Tcm-tetrofosmin imaging for discriminating between malignant mass and benign mass in palpable breast lesions was 87%, specificity 84%, positive and negative predictive value were 85% and 86% respectively. Conclusion The results suggested that 99Tcm-tetrofosmin imaging is a valuable tool for distinguishing between malignant mass and benign mass in palpable breast lesions.