The well-known prognostic factors for breast cancer, such as axillary lymph node status, do not always account for the exact outcome. The development of other accurate prognostic factors would help in assessing high risk for the disease recurrence and death. Recently, there are reports that peritumoral lymphatic vessel invasion is a good prognostic factors to solid tumors in animal studies and clinical trials. This study was performed to estimate the significance of peritumoral lymphatic vessel invasion (PLVI) as a prognostic factor in breast cancer. Also, PLVI was compared withb establishwd established clinicopathological prognostic factors and hormone receptors. MATERIALS AND METHODS: A group of patient was selected from the Department of Surgery, College of Medicine, Hallym University, which consists of 43 out of 96 patients who received curative operation from 1985 to 1993. Peritumoral lymphatic vessel invasion by tumor cells on H&E stain was considered PLVI positive. We classified 43 breast-cancer patients into 32 with negative PLVI and 11 with positive PLVI. We estimated the correlation between the PLVI and other established prognostic factors. We also calculated survivals based on PLVI. RESULT: The 4-year disease-free survival rate was 61.8+/-.7%, and the 4-year overall survival rate was 73.0+/-.0%. The receptor status of estrogen and of progesterone had significant impacts on survival (ER: p=0.0001, PR: p=0.0001). Also, metastasis status of lymph node had significant impacts on overall survival (p=0.0148). We found a significant correlation between PLVI and tumor size (p=0.004), estrogen receptor (p=0.002), progesterone receptor(p=0.006), but could not find any significant correlation between PLVI and menopausal status, histologic grade, unclear grade, lymph node metastasis. PLVI status was correlated with disease free survival rate (p=0.01) and overall survival rate(p=0.01). CONCLUSIONS: The determination of PLVI in breast cancer tissue may be useful as a prognostic factor, but it is necessary to investigate the PLVI in a large number of patients before this conclusion can be stated with certainty.