Surrogate typing of breast cancer, based on quantitative immunohistochemical (IHC) analysis of the expression of estrogen re-receptor (ER) and progesterone re-ceptor (ER), receptor to epidermal growth factor type 2 (Her2/neu) and prolifera-tion index (Ki-67 index), is the "gold standard" in the choice of treatment tactics and assessment of prognosis in breast cancer patients. The widespread introduction of immunohistochemical typing of breast cancer has significantly improved the ac-curacy of choice and effectiveness of drug therapy, as well as survival rates. 

Despite the fact that surrogate typing of breast cancer is traditionally performed once on trepanobiopsy material, it is worth noting that in recent years, repeated de-termination of the surrogate tumor subtype on surgical material has become in-creasingly common in clinical practice. Despite the initially dominant concept that the level of expression of surrogate markers of breast cancer remains unchanged during the entire course of the disease, the results of studies show the contrary.

The aim of our study was to evaluate the prognostic significance of the surrogate subtype of breast cancer determined by immunophenotyping of cor-biopsy and surgical material.