Abstract: Objective To evaluate the ability of diffusion-weighted imaging（DWI） to diagnose axillary lymph node metastases in patients with breast cancer. Methods Preoperative conventional MR and DWI imaging was performed on 24 patients with breast can-cer and enlarged axillary lymph nodes.The apparent diffusion coefficient （ADC） of axillary lymph nodes was determined，and its rela-tionship to histopathologic findings was analyzed. Results The ADC value of metastatic lymph nodes （0.796±0.171） ×10^-3mm²/s was significantly lower than that of benign nodes（1.058±0.234，P<0.05）×10^-3mm²/s.With the threshold ADC value at 0.854×10^-3mm²/s for diagnosing lymph node metastasis，the sensitivity，specificity and accuracy were，respectively，73.91%，86.96% and 80.43%. Conclusion DWI is useful for detecting axillary lymph node metastases in patients with breast cancer.

Key words:  Breast cancer, Lymph node, Diffusion-weighted imaging, Apparent diffusion coefficient