SOX4 and neoplasm: We subsequently performed an overall differential gene expression analysis of antibody-secreting cells from IBC and nIBC, and found that the antibody-secreting cell subpopulation (C4, C11) enriched in IBC tumours specifically expressed high levels of the SOX4 gene (Extended Data Fig. S3d) and that the antibody-secreting cell subpopulation C4 exhibited broad expression of a wide range of molecular markers of immune cells (Extended Data Fig S3e).