Strikingly, it showed that IGHG4 and IGKC were predominantly expressed in HER2neg TNBC group (in tumor tissues containing tumor cells and mesenchymal cells), whereas APOD and MUCL1 were highly expressed in HER2low group (Fig. 4D, E), which were consistent with the scRNA-seq data. This evidence concerns the gene MUCL1 and neoplasm.