We evaluated the associations between tumor‐infiltrating lymphocytes (TIL) including CD8‐positive [+] lymphocytes in ductal carcinoma in situ (DCIS) and histopathologic factors, particularly spontaneous “healing” and immunohistochemical (IHC)‐based subtypes, to clarify the effects of host immune response to cancer cells proliferation during early carcinogenesis for the breast cancer. This evidence concerns the gene CD8A and ductal breast carcinoma in situ.