CD4 and neoplasm: Key newly identified subsets include atypical MBCs, expressing markers like ITGAX and FCRL5, with an exhausted phenotype and progenitor potential for extrafollicular-derived antibody-secreting cells (ASCs); tumor-associated atypical B cells, which interact with CD4+ T cells and predict favorable prognosis; and heterogeneous MBCs (1, 5).