Collovà et al. analyzed the lymphocyte trend in patients with breast cancer undergoing dose-dense chemotherapy with pegfilgrastim and reported that B (CD19+, CD20+) and early B lymphocyte subsets (CD20+/CD38+) decreased significantly during chemotherapy, whereas T lymphocyte subsets did not present significant changes, except for a decrease in T helper (CD4+) cells. This evidence concerns the gene CD4 and breast cancer.