Introduction:
Globally, breast cancer is the most frequently diagnosed cancer in women. Tumor microenvironment (TME), soluble, cellular and physical components plays a pivotal role in tumor progression. Tumor infiltrating lymphocytes (TILs( in ductal carcinoma in situ (DCIS), with and without invasive carcinoma is an emerging area of clinical research. Recent studies have linked high FOXP3 expression in T regulatory (Treg) tumor infiltrating lymphocytes (TILs) with higher grade and stage and poor clinical outcome. CD8+ cytotoxic T lymphocytes have antitumor effects by induction of tumor cell cytostasis, apoptosis, angiostasis and macrophage tumoricidal activity.Thus, examination of the balance between CD8+ and FOXP3+ T cells is crucial in breast cancer prognosis.
Aim of the Work:
The current work was carried out to evaluate the expression of CD8 and FOXP3 in DCIS and invasive breast cancer as well as CD8/FOXP3 ratio in relation to clinicopathological parameters.

Material
The present study comprised 70 retrospective cases of breast cancer .Paraffin blocks of these cases were obtained from the archives of the Pathology Department, Faculty of Medicine, Alexandria University, from January 2018 till December 2022.