OBJECTIVE To observe and subtype the appearance of intraductal papilloma (lesions) and of infiltrating ductal carcinoma or early infiltrating ductal carcinoma using a fiberoptic ductoscope (FDS) examination, and to discuss the differentiation and diagnosis of benign and malignant tumors by FDS.METHODS The characteristics of FDS images and diagnostic data for 229patients with intraductal papilloma (lesions) and 50 patients with ductal carcinoma, who were confirmed by surgical pathology from October 1998 to December 2003, were analyzed retrospectively.RESULTS The appearance of the lesions observed by FDS were grouped into 4 types: a monothelia (type Ⅰ), polythelia (type Ⅱ), superficies (type Ⅲ)and a mixture (type Ⅳ). Intraductal papillomas (lesions) were more commonly seen in type Ⅰ and Ⅱ, and intraductal carcinomas or early infiltrating ductal carcinomas were more commonly seen in type Ⅲ and Ⅳ;there was a statistically significant difference in the distribution of the ductoscopic types, except in type Ⅱ, between the two types of lesions, P＜0.001. The focal detection rate by FDS for intraductal papilloma and papillomatosis was 99.6% (228/229) and for breast cancer was 96.0% (48/50). The diagnostic accuracy was 97.8% (224/229) and 82.0% (41/50),respectively.CONCLUSION FDS can be a guide for the treament of benign and malignant intraductal tumors, with early discovery and accurate diagnosis.