Abstract: Objective To investigate the diagnostic value of neutrophil lymphocyte ratio in intraductal papillary neoplasms (IDPN)of breast. Methods Clinical data about patients diagnosed as intraductal papillary neoplasms of breast from July 2014 to June 2016 were analyzed retrospectively in Breast Disease Center, Chinese PLA General Hospital.The patients were divided into benign group and malignant group according to postoperative pathologic results, and neutrophil lymphocyte ratio (NLR), age, menopause, nipple discharge and tumor size in each group were compared.Furthermore, the optimal cut-off value of NLR in the differentiation of benign and malignant neoplasms was obtained by ROC curve. Results A total of 175 patients were diagnosed as intraductal papillary neoplasms of breast.There were 122 (69.71%) cases diagnosed as intraductal papilloma and 53 (30.29%) cases diagnosed as intraductal papillary carcinoma.NLR values were (1.76±0.78) in benign group and (2.60±1.14) in malignant group, respectively(P＜ 0.05).NLR was the main factor associated with the classi fication of IDPN (P＜ 0.05).The optimal NLR cut-off value obtained from ROC analysis was 1.90 with AUC of 0.766, sensitivity of 77.40%, speci ficity of 67.20%, positive predictive value of 84.45%and diagnostic accuracy of 74.31%, respectively. Conclusion Preoperative NLR is helpful to differentiate malignant intraductal papillary neoplasm of breast from benign tumor, and high NLR is a signi ficant diagnostic predictor of breast cancer.