Abstract: Objective To compare the features of high frequency color Doppler ultrasound between infiltrating ductal carcinoma and non-lactation mastitis. Methods A total of 116 non-lactation mastitis cases（71 ultrasound-diagnosed non-lactation mastitis and 45 non-lactation mastitis misdiagnosed as cancer） and 115 infiltrating ductal carcinoma cases were analyzed retrospectively to compare their ultrasound features. Results Non-lactation mastitis group showed regular shape，clear boundary，no echo area，and posterior echo enhancement，and the difference was statistically significant compared with the misdiagnosed group（P<0.05）. Compared to infiltrating ductal carcinoma group，non-lactation mastitis group displayed regular shape，clear boundary，less speckle strong echo，no echo area，less hyperechoic halo，posterior echo enhancement，and less axillary nodes（P<0.05）. Infiltrating ductal carcinoma group and misdiagnosed group showed similar ultrasound features including irregular shape，unclear boundary，heterogeneous echo，and enriched blood supply，but displayed statistically significant of speckle strong echo（χ²=30.805，P<0.001），hyperechoic halo（χ²=20.282，P<0.001），and posterior echo enhancement （χ²=6.442，P=0.011）. Conclusions Non-lactation mastitis is easily misdiagnosed as infiltrating ductal carcinoma diagnosis by high-frequency color Doppler ultrasound. Attention to the observation of spotted strong echo，high echo halo，and rear echo enhancement are helpful for its correct diagnosis.

Key words: Infiltrating ductal carcinoma, Non-lactation mastitis, High frequency color Doppler ultrasound