Abstract: Objective To explore the mechanisms of the effect of mast cell(MC) on lymphangiogenesis and lymph node metastasis via detecting the expressions of VEGF-C in MCs of invasive breast ductal carcinoma. Methods Double immunohistochemical– histochemical reactions were used to detect the expressions of VEGF-C in MCs in breast benign disease and invasive ductal carcinoma.VEGF-C in breast benign disease and invasive ductal carcinoma were measured by SP methods and the lymphatic vessels were marked by D2-40 for count. Results The quantities of the MCs without the dark blue VEGF-C particles in breast benign disease(7.80±1.22) were fewer than that with the dark blue VEGF-C particles in invasive ductal carcinoma(15.44±2.39,P<0.01).There were also significant difference among the Ⅰ,Ⅱ,Ⅲ grading of invasive breast ductal carcinoma(10.75±2.61,13.70±1.92,15.33±0.62,P<0.01).The VEGF-C expression of MCs in the carcinoma was significantly stronger than that in benign disease(P<0.01),but there was no correlation between the expression of VEGF-C in MCs and that in cancer cells.The quantities of the MCs and LVD of perim-carcinoma in invasive ductal carcinoma with lymph node metastasis(14.03±2.01,11.21±4.60)were significantly higher than that in invasive ductal carcinoma without lymph node metastasis(11.22±0.55,5.78±3.02,P<0.01).The quantities of the MCs were correlated positively with the quantities of lymphatic vessels in breast carcinoma (r=0.18). Conclusion The expressions of VEGF-C in the MCs could be induced by breast carcinoma,and the quantities of MCs were correlated positively with lymphangiogenesis and lymph node metastasis.