Abstract: Background Lugol’s solution has been successfully applied to esophagus, cervix and oral cavity in order to detect lesion in early carcinoma and precancerous disease. The objective of this thesis is to probe into the value of fiberoptic duct endoscopy (FDS) iodine staining for the diagnosis of intraductal proliferative lesions. Methods Periodic acid Schiff (PAS) staining was first of all to be implemented on fifty-five cases of mammary gland hyperplasia tissue and 57 cases of Invasive breast cancer tissue; In vitro iodine staining was then to be effected on 64 cases of fresh mammary gland hyperplasia tissue and 53 cases of invasive breast cancer tissue; what follows was to select 177 cases of patients with nipple discharge on whom FDS was to be carried out; of the 177 patients 92 were chosen by random and on them endoscopic Lugol's iodine staining should be effected, with the other 85 serving as the control group, whose suspicious lesions should be cut and inspected with wire positioning, thus evaluating the value and clinical significance of Lugol's iodine staining for the diagnosis of intraductal proliferative lesions. Results PAS stainings were positive in mammary gland hyperplasia while PAS positive substance would be gradually eliminated until an neglectable level（P<0.05）, that Mammary gland hyperplasia specimens took on a color of tan brown after supravital staining whereas the color of breast cancer samples after staining got significantly lighter or unstained, and that the detection rate of ductal intraepithelial neoplasia ( DIN )by means of fiberoptic duct endoscopy (FDS) iodine staining was 93.0% and the rate among the control group 70.9%（P<0.05）. Conclusion The detection rate of DIN can be boosted by means of endoscopic breast ductal epithelial iodine staining and this approach deserves to be applied and extended.

Key words: Carcinoma, Ductal, Breast, Endoscopes