Inactivation of the gene "deleted in colon cancer" (DCC) on chromosome 18 is known to be associated with the tumorigenesis and metastasis of colorectal cancer. In the present study, we investigated the expression of DCC, P53 and HER-2/neu product in surgical specimens from 79 patients with invasive breast cancer by immunohistochemistry staining and found the expression of DCC to be decreased in 42 tumors (52%). Overexpression of HER-2/neu and P53 was detected in 29 (36.8%) and 26 (32.9%) of this 79 breast cancer specimens, respectively. To evaluate the outcomes of the 79 breast cancer patients, we followed up the patients during the period from May 1990 to August 1998. The average length of follow-up was 52 months (ranging from 4 to 94 months). Patients with tumors having a combination of DCC-negative and HER-2/neu overexpression showed a marginal influence on survival time of breast cancer (P = 0.06). However, patients with tumors having a combination of DCC-negative and P53 overexpression showed no influence of these on survival time of breast cancer (P = 0.36). These findings suggest that a decreased DCC expression and HER-2/neu overexpression may influence the prognosis of breast cancer.