Abstract: Objective : To investigate the morphologic characteristics of micro-lymphatic vessels marked by D2-40 inhuman breast cancer and to analyze the correlation with metastasis of lymph nodes. Methods : A total of 102cases of breast cancer and 25 cases of breast fibro-adenoma (control group) were collected and all of themunderwent surgery in our hospital from January 2003 to October 2006. The expression of D2-40 and CD31 inlymphatic microvessels was evaluated by single-labeling or double-labeling immunohistochemistry. The lymphatic micovessel density (LMVD) was calculated. The relationship of LMVD with the state of lymph nodemetastasis was analyzed. Results : The positive rate of D2-40 in the 102 breast cancer cases was 76.5% (78/102). The positive rate of D2-40 in the control group was 24% (6/25), obvious lower than that in the breastcancer group (χ²=24.685, P=0.000). The median LMVD in the 102 cases of breast cancer was 21.61 (19.72±5.11) lymphatic microvessels per × 100 field visually, significant higher than that in the control group 5.10(7.10 ± 3.72) lymphatic microvessels per ×100 field visually (t=2.561, P=0.017). Moreover, the LMVD in theperipheral region of breast cancer was significant higher than in the intratumoral region (P<0.01). The statistical Results of one-way ANOVA and Pearson Correlation suggested that the number of lymphatic nodes infiltrated by tumor cells was correlated with LMVD in the peripheral region of breast cancer, but was not correlatedwith the LMVD in the intratumoral region (P<0.01, r=0.964). Conclusion : In human breast cancer, new monoclonal antibody D2-40 can specifically mark the lymphatic endothelial cells. The positive lymphatic microvessels, especially in the peripheral region, are correlated with the lymphatic metastasis of breast cancer, indicating that the suppression of micro-lymphatic vessels may become a new choice of tumor therapy.