Abstract:ObjectiveTo investigate the role of 18F-FDG PET/CT in differnetiating primary breast lymphoma (PBL) from breast cancer in order to improve the correct diagnostic rate of them. Methods 18F-FDG PET/CT images and clinical data of 16 cases of PBL ,25 cases of breast cancer confirmed by pathology were retrospectively analyzed. The manifestations of 18F-FDG PET/CT were observed and the maximum diameter of tumors,the maximal standardized uptake value (SUVmax) and SUVmax/the maximum diamete were measured. Differences of clinical data and imaging indicators between the two groups were compared by using t test and χ2 test. The SUVmax and SUVmax/the maximum diamete values of the two groups were analyzed by using receiver operating characteristic (ROC) curve to determine the optimal threshold and diagnostic efficiency. Results The bilateral and multiple lesions were more common in primary breast lymphoma, the difference was statistically significant (χ2=10.28, 10.66,P=0.001, 0.010). The SUVmax of the PBL and breast cancer groups was (13.02±7.70) and (7.22±4.63) respectively, the difference was statistically significant (t=3.02, P=0.004). The SUVmax/the maximum diamete values of the two groups was (5.69±3.48) and (2.43±1.31) respectively, the difference was statistically significant (t=-4.25, <0.001). On the ROC curve, the sensitivity of SUVmax for the diagnosis of PBL was 93.8%, specificity 52.0% and area under the ROC curve 0.76 with the SUVmax cutoff value of 4.85. The sensitivity of SUVmax/the maximum diamete for the diagnosis of PBL was 76.0%, specificity 75.0% and area under the ROC curve 0.82 with the maximum diameter cutoff value of 2.85. Conclusion 18F-FDG PET/CT has promising potential for the diagnostic differentiation of PBLs and breast cancers. The SUVmax and SUVmax/the maximum diameter of tumors have a high diagnositic performance.