RESUMEN
<p><b>INTRODUCTION</b>This study aimed to analyse the concordance rate, sensitivity, specificity, positive predictive value (PPV) and negative predictive value of core needle biopsy (CNB) and subsequent surgical specimen (SS) in assessing levels of oestrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor 2 (HER2/neu). It also evaluated the revised American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines for ER/PgR positivity.</p><p><b>METHODS</b>We analysed the breast cancer database of KK Women's and Children's Hospital, Singapore, from 1 June 2005 to 30 December 2012. Invasive breast cancer patients who had CNB and subsequent SS were included.</p><p><b>RESULTS</b>A total of 560 patients were included. The concordance of ER, PgR and HER2/neu positivity between CNB and SS was 96.1%, 89.1% and 96.8%, respectively. When the 'ER ≥ 10% positive' group was compared with the 'ER ≥ 1% positive' group, specificity increased from 79.7% to 92.5% and PPV increased from 93.9% to 97.5%. When the 'PgR ≥ 10% positive' group was compared with the 'PgR ≥ 1% positive' group, specificity increased from 84.2% to 89.3% and PPV improved from 89.7% to 92.9%. The revised ASCO/CAP guidelines decreased discordant results by > 50% for ER and by 18.2% for PgR.</p><p><b>CONCLUSION</b>CNB has high concordance with SS in the evaluation of the molecular profile of invasive breast cancer. Thus, molecular evaluation does not need to be repeated with SS except for ER-, PgR- and HER2/neu-negative CNB results. The revised ASCO/CAP guidelines resulted in more precise ER and PgR status on CNB.</p>