Features of tumor heterogeneity in regional metastasis of breast cancer

Abstract

The review looked at the issues of tumor heterogeneity in breast cancer. Tumor heterogeneity is classified according to the main feature demonstrating regional differences within a tumor (for example, heterogeneity of clinical manifestations, histological heterogeneity, heterogeneity of protein expression, etc.) and by tumor regions (differences between primary tumors and metastases, differences between cell clones within a single tumor node, etc.). Temporal heterogeneity is also distinguished, which manifests itself in the clonal evolution of tumor cells. The review covers the heterogeneity in the expression of four biomarkers from the gold standard for immunohistochemical staining of breast cancer: estrogen receptors, progesterone receptors, Her2/neu and Ki67 in primary tumor tissue and regional metastases. According to various studies, discordance in estrogen receptor status of primary tumor cells and metastases was observed with a frequency of 4 to 62%, progesterone receptors from 12 to 54%, Her2/neu from 0 to 24%, Ki67 from 4 to 39%. The results of studies of changes in the expression levels of individual markers in breast cancer metastases, as well as the heterogeneity of surrogate subtypes of tumor tissue in metastasis, are briefly described. Possible reasons for heterogeneity in the expression of key prognostic and predictive markers by primary tumor and metastatic cells, such as artificial factors at the preanalytic and analytic stages of the study, polyclonality of the primary tumor before metastasis, clonal evolution of tumor cells during metastasis, selection of tumor clones under the therapy are highlighted.