CD4 and neoplasm: CD8+ cytotoxic T lymphocytes increase anti-tumour immunity, and CD4+ helper T cells play critical roles in adaptive immune response along with B lymphocytes and CD8+ cytotoxic T cells.27–29 However, exhausted CD8+ T lymphocytes and regulatory T cells (Treg; subset of CD4+ T lymphocyte) suppress anti-tumour immunity.30,31 Therefore, the immune response to breast tumour could vary depending on the composition of lymphocytes, which ultimately affects prognosis.