PURPOSE: We aimed to assess the concordance of the immunohistochemical profiles of core biopsy before administrating neoadjuvant chemotherapy with that of the surgical specimens after a definitive operation for breast cancer. METHODS: We retrospectively reviewed the estrogen receptor (ER), progesterone receptor (PR), and HER-2 expressions in 130 consecutive patients who received neoadjuvant chemotherapy and were followed by surgery during the period between February 2002 and March 2006. The pathologic complete tumor response rate for this group was 4.6% (6/130). Both the pre- and post-operative immunohistochemical profiles were available in 32 of the 124 patients (25.8%). Immunohistochemical staining was done on the core biopsies before chemotherapy and on the surgical specimens after operation. RESULTS: There were 12 markers from 11 patients that were altered out of the 96 total markers (ER, PR, or HER-2) from 32 patients: 2 ER (2/12, 16.7%), 4 PR (4/12, 33.3%), and 6 HER-2 (6/12, 50.0%). One patient simultaneously had changes in the expressions of PR and HER-2. Conversion of the hormone receptor status occurred in 3 patients (3/32, 9.4%): this was positive to negative in two, and vice versa in one. In addition, there were 6 conversions (6/32, 18.8%) of the HER-2 status from negative to positive. CONCLUSION: The hormone receptor status changed in 9.4% of the 32 patients and the HER-2 status changed in 18.8% of the 32 patients after neoadjuvant chemotherapy. We have concluded that conducting only a single immunohistochemical study about ER, PR, and HER-2 may not be enough to exactly estimate the tumor marker status in the neoadjuvant setting.