Receptor discordance between primary tumors and nodal metastases and correlation with the 21-gene recurrence score in early-stage, estrogen receptor-positive, node-positive breast cancer. - Zheng S; Sullivan P; Vadehra K; Kim J; Levee A; Callahan R; Teshome M; Tseng CH; Bardia A; Kapoor NS (Breast cancer research and treatment, 2026)