Change in the Phenotype of Breast Cancer After Treatment

Breast cancer ranks first in mortality among cancer diseases in women. This figure is not decreasing, despite new data being obtained annually on the morphology of breast cancer and advances in its treatment. According to global standards, in order to prescribe effective treatment, it is necessary to know the phenotype of the tumor which is determined by the expression of a number of markers, such as estrogen and progesterone receptors (ER, PR), HER2/neu and Ki 67. According to numerous studies, it has been revealed that native, residual, recurrent and metastatic tumors may differ in phenotype, regardless of the initially established variant. In addition, changes in the immunophenotype of the tumor are also affected by the treatment performed. At the moment, enough data have been accumulated around the world confirming the possibility of changing the tumor phenotype. However, to date, there are no standards regulating the additional IHC studies after treatment, or when a recurrent/metastatic lesion is detected. Carrying out additional immunophenotyping of the tumor can help reduce the likelihood of prescribing ineffective treatment and select the most optimal therapy in each specific case.