Lymph vessel tumor emboli (LVTEs) within tumors are difficult to distinguish from stroma-invasive tumor foci. The purpose of this study was to evaluate staining of LVTEs with hematoxylin-eosin (HE) and with D2-40 to determine whether LVTEs identified by HE staining alone are D2-40-positive LVTE and whether the presence of LVTE identified by HE or D2-40 staining is an accurate predictor of outcome in 151 patients with invasive ductal carcinoma (IDC) of the breast. We first attempted to identify LVTE in the stroma-invasive tumor area (intratumor area), the advance area, and the nontumor area by HE staining alone, and then LVTE identified by HE staining was confirmed by D2-40 staining. The number of LVTE identified by HE staining and D2-40 staining successively increased from the intratumor area to the nontumor area. Although D2-40 staining detected larger numbers of LVTE than HE staining in all tumor areas, the highest positive predictive value of LVTE was observed in the intratumor area, and the next was in the advance area, and then the nontumor area, and significant correlations were found between the numbers of LVTE stained by HE and D2-40 in the same tumor areas. LVTE identified by HE staining or D2-40 staining in the intratumor area or nontumor area significantly increased the risk for tumor recurrence or death of patients with IDC, independent of hormone receptor status or nodal status. The results of this study demonstrate that the existence of intratumoral LVTE and that the presence of intratumoral LVTE identified by HE staining or D2-40 staining are accurate predictors of the outcome of patients with IDC of the breast.