Breast cancers are a large heterogeneous group of malignant epithelial neoplasms originating from breast glandular tissue. With the exception of skin cancer, breast cancer is the most commonly diagnosed malignant tumor in women, with an incidence of 24.2 % and the leading cause of death from malignant diseases. Triple negative breast cancer (TNBC) is immunohistochemically ER, PR and HER2 negative. It accounts for about 15 - 20 % of breast cancers. Compared to other breast cancers, TNBC is more aggressive in nature, has a high potential for metastasis and a poor clinical outcome. Tumor microenvironment (TME) is the cellular environment of tumor cells or tumor stem cells. It consists of various components: immune cells (granulocytes, lymphocytes, macrophages), fibroblasts, pericytes, adipocytes, blood vessels, ECM and signaling molecules. Complex interactions between tumor cells and the immune system are called immune regulation. Immune regulation means the dual role of the immune system - the role of protecting the host and the role in tumor growth and development. Non-malignant cells in TME often play an antitumor role in carcinogenesis. Since they affect tumor development, TME components (such as immune cells) are important in assessing tumor prognosis as well as in selecting appropriate treatment.