In this study, the CD4+CD25+ T cells CDR3 repertoires in breast tumor tissues and lung metastatic tissues were roughly the same with respect to the diversity of the CDR3 repertoires, high-frequency clone proliferation, composition of the CDR3 and the overlapping ratio, and public CDR3 sequences, but they were different from that in spleens. The gene discussed is CD4; the disease is breast neoplasm.