VTCN1 and breast neoplasm: Recent studies have also intriguingly identified high expression of B7-H4, a PD-L1 family member, on tumor cells of poorly immune infiltrated breast tumors.17 However, the receptor for B7-H4 (analogous to PD-1 and presumably present on T-cells, which are suppressed in the presence of B7-H418) has not yet been defined, despite the clinical development of B7-H4-blocking antibodies.