Hormone Receptors and HER2 Expression in Primary Breast Carcinoma and Corresponding Lymph Node Metastasis: Do we Need Both?

Background: Scattered studies report on controversial results concerning evaluation of primary breast tumors and their matched lymph node metastases. Aim. To investigate the molecular profile of primary breast tumors and corresponding lymph node metastases (LNM) based on estrogen receptor (ER), progesterone receptor (PR) and human epiderma growth factor receptor-2 (HER2 protein). Materials and Methods: Sixty-six primary tumors and corresponding axillary lymph node metastases were evaluated by immunohistochemistry for ER, PR and HER2 protein. According to these markers, cases were stratified as Luminal A, B, HER2 subtypes and triple-negative. Results. Thirteen out of 66 cases (19.7%) exhibited different tumor cell phenotypes in nodal metastases compared to primary breast tumors. All cases with hybrid phenotype had metastases with a pure HER2 phenotype. The most frequent switching was observed from luminal A to luminal B phenotype. Conclusion: The high rate of discrepancy between primary tumor and nodal metastasis phenotype imposes the need for a comparative assessment of both primary tumor and nodal metastasis before any therapeutic decision, in order to avoid recurrence and to improve patient prognosis and overall survival.