Immune microenvironment and intrinsic subtyping in hormone receptor-positive/HER2-negative breast cancer.

Little is known regarding the interaction between immune microenvironment and tumor biology in hormone receptor (HR)+/HER2- breast cancer (BC). We here assess pretreatment gene-expression data from 66 HR+/HER2- early BCs from the LETLOB trial and show that non-luminal tumors (HER2-enriched, Basal-like) present higher tumor-infiltrating lymphocyte levels than luminal tumors. Moreover, significant differences in immune infiltrate composition, assessed by CIBERSORT, were observed: non-luminal tumors showed a more proinflammatory antitumor immune infiltrate composition than luminal ones.