Inflammation in the tumor microenvironmentisanessentialaspectof tumor biologicalactivity. Interferon γ and IL-10 are pro-inflammatoryand anti-inflammatorycytokinesthatplay a crucialrole in regulatingthehost'simmuneresponseto cancer cells. IFN-γ and IL-10 expression are associatedwithpoor prognosis andlowsurvivalrate in breastcarcinomapatients. This cross-sectional study was performed on the 60 paraffin-embedded samples of radical mastectomy during January 2016-December 2019 at Anatomical Pathology Laboratory of Dr. Soetomo General Academic Hospital Surabaya. The samples were divided based on tumor size into four groups (T1, T2, T3, T4). TheanalyzedwasusingKruskal Wallistest. Immunohistochemical staining was performed to detect the expression of IFN-γ and IL-10. There was a significant difference in IFN-γ expression in the four groups (p=0.005) and no significant difference in IL-10 expression in the four groups (p=0,191). Interferon gamma and IL-10 were important in determining prognosis and targeted therapy in breast cancer patients. These results may contribute to the development of breast cancer research.