Correlation of Human Epidermal Growth Factor Receptor 2 (HER2), Estrogen Receptor (ER), and Progesterone Receptor (PR) Expression as Predicted by Core Biopsy with the Immunohistochemical Results of Surgical Breast Cancer Specimens

Representative breast cancer specimens can be obtained by core biopsy. Immunohistochemistry (estrogen receptor: ER, progesterone receptor: PR, and human epidermal growth factor receptor 2: HER2) of core specimens and excised tumors should correlate. Antigen retrieval and tumor heterogeneity may impair immunohistochemical procedures and lead to unreliable results. Patients and Methods: Data was collected from 110 patients with operable invasive breast cancer who were diagnosed by core biopsy between 2001 and 2006, subsequently underwent primary surgery, and had complete immunohistochemical evaluation of biopsy and surgical specimens. ER, PR, and HER2 status were semiquantitatively evaluated. Results: Categorical ER and PR expression correlated in 54% and 55%, respectively. Clinically relevant ER status (positive versus negative) correlated in 97% and the PR status in 88%. HER2 overexpression was observed in 18% of core biopsies and 28% of surgical specimens with a concordance in 69%. Correlation of categorical HER2 expression (0, 1+, 2+, 3+) was present in only 46%. Conclusion: In our patient population, steroid hormone receptor status could be predicted by core biopsy. However, the rather weak concordance of the HER2 status must be further examined. To evaluate whether core biopsies or surgical specimens are better suited to predict the more accurate HER2 status, gene amplification of both specimens should be correlated. Until then, diagnosis of HER2 expression in core biopsy specimens should be interpreted with care.