The vascular endothelial growth factor (VEGF) appears to play an important role in tumor angiogenesis. The p53 and HER-2/neu genes have been thought to regulate VEGF expression. Although the most common genetic alterations described in human breast cancer are p53 gene mutations and HER-2/neu gene amplification, there is a paucity of reports concerning a possible association between VEGF expression and p53 and HER-2/neu expression. Ninety-nine invasive ductal carcinoma cases were examined by immunohistochemical studies with anti-VEGF, anti-p53, anti-HER-2/neu, and anti-CD34 antibodies. Computerized image analysis was used to evaluate the microvessel density (MVD). Eighty-eight tumors (88.9%) were classified as being VEGF positive. Twenty-five tumors (25.3%) showed p53 protein expression, while 36 tumors (35.4%) expressed the HER-2/neu protein. The MVD ranged from 22.0 to 197.0, with a median value of 58.5 (65.4 +/- 27.9). The tumors expressing VEGF had a significantly higher MVD than those that did not (P < 0.05). VEGF expression was significantly associated with p53 protein expression (P < 0.01). In double VEGF and p53 immunohistochemical stained sections, the two markers were generally expressed in the same tumor cells. The cancer stage was the only independent prognostic factor of disease-free and overall survival. The authors' results suggest that VEGF expression plays a role in promoting angiogenesis in invasive ductal carcinoma of the breast, and p53 is likely to be involved in regulating VEGF expression.