Among the group of biochemical parameters, catalase activity was most significantly reduced in the luminal breast cancer subtypes: luminal A (−19.2%, p = 0.0201), luminal B(−) (−24.0%, p = 0.0036), and luminal B(+) (−34.9%, p = 0.0130) compared with the healthy controls. Here, CAT is linked to breast carcinoma.