Objective·To explore the association between breast atypical ductal hyperplasia （ADH） and breast cancer. Methods·A total of 442 benign and malignant breast samples were collected, including 253 invasive carcinoma samples, 79 noninvasive carcinoma (ductal carcinoma in situ, 25 low grade carcinoma and 54 high grade carcinoma) samples, and 110 benign samples. Histological characteristics and immunohistochemical changes of ADH were observed. The detection rates of ADH in different types of samples were statistically analyzed. Results·The diameters of ADH were all less than 2 mm. Lumens cells were negative for CK5/6 and myoepithelial cells were positive for p63. The detection rate of ADH in noninvasive carcinoma samples was significantly higher than those in benign samples and invasive carcinoma samples (both P=0.000). The detection rate of ADH in low grade noninvasive carcinoma was significantly higher than those in invasive carcinoma samples and high grade noninvasive carcinoma (both P=0.000). Conclusion·Breast ADH is closely associated with ductal carcinoma in situ. Timely detection and removal of ADH are important for preventing breast cancer.