Igari F, et al. - The diagnostic importance of intratumoral CD8+ tumor infiltrating lymphocytes (TILs) in medullary carcinoma (MC) was determined. In the current study it was shown that extensive intratumoral CD8+ TIL infiltration serves as a promising biomarker for distinguishing MC from lymphocyte-predominant breast cancer (LPBC), particularly in non-luminal type cancers.