OBJECTIVE To investigate the relationship between lymphatic vessel density and lymph node metastasis of invasive micropapillary carcinoma (IMPC) of the breast.METHODS The immunohistochemical study for vascular endothelial growth factor-c (VEGF-C), VEGF Receptor-3 (VEGFR-3) and lymphatic vessel density of 51 cases of IMPC were performed, and lymph node metastases were examined by microscopic analysis of these cases.RESULTS In IMPC, VEGF-C was expressed in the cytoplasm and/or on the membrane of the tumor cells, and the expression of VEGF-C showed a positive correlation with lymph node metastasis (P＜0.01). Lymphatic vessel density was determined by the number of micro-lymphatic vessels with VEGFR-3 positive staining. Lymphatic vessel density was positively correlated with VEGF-C expression (P＜0.01) and lymph node metastasis (P＜0.01). The percentage of IMPC in the tumor was not associated with the incidence of lymph node metastasis. The metastatic foci in lymph nodes were either pure or predominant micropapillary carcinoma.CONCLUSION The results suggested that VEGF-C overexpression stimulated tumor lymphangiogenesis, and the increased lymphatic vessel density may be the key factor that influenced lymph node metastasis of IMPC.