MONITORING THE DYNAMICS OF BREAST CANCER HETEROGENEITY THROUGH IMMUNOHISTOCHEMICAL PROFILING: CASE STUDIES FROM CLINICAL PRACTICE

Breast cancer is a biologically heterogeneous disease with variable responses to therapy. The aim of this study was to demonstrate the clinical importance of monitoring changes in the immunohistochemical profile. A retrospective analysis of four patient cases treated at one oncology center was conducted. During therapy, changes in tumor subtypes were identified, including transitions from triple-negative to HER2-low or luminal types, as well as shifts from hormone receptor–positive to hormone receptor–negative disease. These alterations required substantial adjustments in therapeutic strategies, such as discontinuation of endocrine therapy, initiation of CDK4/6 inhibitors, or the addition of HER2/neu-targeted agents. The results indicate that dynamic monitoring of the IHC profile is a practical and effective method that may enhance personalized therapy in the Republic of Kazakhstan.