Receptor discordance among primary tumors, brain metastases and extra-brain metastases in patients with breast cancer.

Background: To investigate the expression status of estrogen receptor (ER), progesterone receptor (PR) and HER2 in patients with breast cancer brain metastases (BM). Methods: Patients who underwent craniotomy for BM were included. The status of ER, PR and HER2 (including HER2-low expression) in primary breast tumors (PT), BM and extra-BM (EM) was determined. Results: Between PT and BM, conversion of hormone receptor and HER2 occurred in 28% (30/107) and 12% (10/86) of cases. When considering three-tiered categorization of HER2, the conversion rate reached 31%. In the paired EM and BM (n = 39), the discordance rates were 18%, 3% and 22%, respectively. Conclusion: Receptor discordance was dynamic and relevant, especially using new HER2 categorization.