CEST-mDixon imaging utilizing hydroxyl and amine pools could aid breast tumor diagnosis, as shown in previous preliminary studies. In the current study, CEST-mDixon is evaluated in a breast cancer patient cohort using improved saturation and acquisition parameters. The results agree with previous findings demonstrating moderate linear correlation of CEST effects at 1 ppm and 2 ppm with Ki-67. In addition, we observe a linear correlation with the percentage of cells positive for nuclear expression of the progesterone receptor (PR), the first such observation reported. Overall, the study confirms the potential for CEST-mDixon for characterizing breast tumor aggressiveness non-invasively.