CD19 and breast cancer: For instance, TIBs can be observed in all stages of human lung cancer development, and their presence differs between stages and histological subtypes.[37] In breast cancer, the frequencies of CD19+‐IL‐10+ B reg cells correlated with shorter OS, and the coexistence of B reg cells with regulatory T cells correlated with shorter metastasis‐free survival.[38] TIBs consist of different subpopulations with opposite functions.