Abstract only e12037 Background: Neoadjuvant chemotherapy(NAC) is the accepted approach for women with locally advanced breast cancer with technically inoperable disease. Systemic treatment is mainly based on the presence of the Estrogen (ER) receptor, Progesterone (PR) receptor and HER2 status on the core needle biopsy prior to treatment. Previously, discordance of the hormone receptor (HR) status was reported as 8-33% in the breast cancer patients after NAC. In here, we evaluated the HR and HER2 discordance after NAC in locally advanced breast cancer patients. Methods: We reviewed the data of 849 breast cancer patients retrospectively. The pathological specimens of core needle biopsy and operation specimens were re-evaluated for HR and HER2 status in 38 patients who had been treated with NAC. The changing of HR and HER2 status after chemotherapy was defined as discordance. The relationship between clinicopathological parameters and discordance and significance of them for disease-free survival (DFS) was analyzed by chi-square and univariaty test. Results: Over 80% of patients were clinically stage III breast cancer. Out of 24 patients were premenapouse and median age was 44.5(30-94). The patients were received median 4(1-6) cycles of NAC as 2 of them were only hormonotherapy, 8 were only antracycline and others were both antracycline and taxanes. Nearly 80% of patients were performed modified radical mastectomy(MRM).Postoperatively median tumor size was 1.6cm(0-10) and median dissected lymph nodes was 14(0-28). After operation, 4(10.5%), 8(21.1%) and 8(21.1%) discordance were detected for ER, PR and HER2 respectively. While HER2 discordance were related with recurrence(p=0.01) and PR discordance(p=0.04), ER discordance was related with only patological stage(p=0.03). At the median follow-up of 15.7 months, 5 year DFS rate and time were 30% and 30.4 months(18.7-42.2), respectively. Operation type, stage, lymphovascular invasion, perineural invasion were found to be significant for DFS, HR and HER2 discordance was not related with DFS. Conclusions: Until more definitive results will be obtained from future studies, receptor status of the residual tumor after NAC should be retested.