Alterations in Hormonal Receptor Expression and HER2 Status between Primary Breast Tumors and Paired Nodal Metastases: Discordance Rates and Prognosis

Background: We aimed to evaluate the estrogen receptor (ER), progesterone receptor (PR), and humanepidermal growth factor receptor 2 (HER2) expression discordance in matched pairs of primary breast cancerand lymph node metastasis specimens and determine the effect of discordance on prognosis. Materials and
Methods: Among all patients diagnosed with lymph node metastases from 2004 to 2007, primary tumors andpaired lymph node metastases were resected from 209 patients. The status of ER, PR, and HER2 expressionwas analyzed immunohistochemically in 200, 194, and 193 patients, respectively. Discordance was correlatedwith prognosis.
Results: Biomarker discordance between primary tumors and paired lymph node metastaseswas 25.0% (50/200) for ER status, 28.9% (56/194) for PR status, and 14.0% (27/193) for HER2 status. ERpositivity was a significant independent predictor of improved survival when analyzed in primary tumors andlymph node metastases. Patients with PR-positive primary tumors and paired lymph node metastases displayedsignificantly enhanced survival compared to patients with PR-positive primary tumors and PR-negative lymphnode metastases. Patients with ER- and PR-positive primary tumors and paired lymph node metastases whoreceived endocrine therapy after surgery displayed significantly better survival than those not receiving endocrinetherapy. Similalry treated patients with PR-negative primary tumors and PR-positive paired lymph nodemetastases also displayed better survival than those not receiving endocrine therapy.
Conclusions: Biomarkerdiscordance was observed in matched pairs of primary tumors and lymph node metastases. Such cases displayedpoor survival. Thus, it is important to reassess receptor biomarkers used for lymph node metastases.