ERBB2 and breast cancer: This study evaluates four CEST postprocessing metrics—MTRasym, Lorentzian amplitudes, MTR relaxation exchange (MTRREX), and apparent exchange-dependent relaxation (AREX)—for their diagnostic performance in differentiating BC subtypes using endogenous APTw-CEST and exogenous 2-deoxy-D-glucose-CEST in a murine BC xenograft model of Luminal A, human epidermal growth factor receptor 2 (HER2)+, and triple-negative tumors.