Heterogeneity between core needle biopsy and synchronous axillary lymph node metastases in early breast cancer patients: Comparison of HER2, estrogen and progesterone receptor expression profiles during primary treatment regime.

e12565 Background: Therapeutic decisions for the primary treatment of breast cancer is commonly based on the expression profiles of estrogen (ER), progesterone (PR) and the human epidermal growth factor 2 (HER2) receptors. However, breast cancer is a very heterogeneous disease, and receptor changes were manifold reported during progression. Little is known about receptor discordance in the primary setting. Here, we compared receptor expression profiles between core needle biopsy (CNB) of the breast tumor tissue and synchronous axillary lymph node metastases (LNM) not at recurrence, but at the primary treatment. Methods: In a German single center study, we retrospectively analyzed 175 breast cancer patients with axillary synchronous LNM. 69,7% of our patients were without any upfront therapy. Profiles of ER, PR and HER2 were immunohistochemically analyzed using the common cut-off at 10% positive tumor cells vs. the controversially discussed low-positive cut-off at 1%. Receptor status was compared between CNB specimens of the primary tumor tissue and axillary LNM. Further, clinicopathological characteristics were correlated to receptor changes. Results: The discordance rates between CNB and axillary LNM were 12.7% for HER2, 6.9% for ER and 22.6% for PR using the ≥1% cut-off, respective 7.5% for ER and 25.6% for PR when using the ≥10% cut-off-level. The most frequently occurring change was a PR loss. Analysis of clinical parameters revealed a significant association of ER change between CNB and LNM in younger patients (p < 0.01) with increased proliferation marker Ki-67 (p = 0.04). Conclusions: Receptor discordance between CNB and synchronous axillary LNM appears to exist at the primary setting already. Hence, receptor profiles of the tumor tissue and the synchronous axillary LNM should be considered for treatment decision.