Further analysis of breast cancer patients with different molecular subtypes revealed that ARID1A expression was significantly lower in eMDSCshigh luminal A breast cancer (p = 0.0369, Figure 4D), rather than in the luminal B, HER2 and Basal-like subtype (p = 0.0917, p = 0.4872, p = 0.3361, Figures 4E–G). This evidence concerns the gene ERBB2 and breast carcinoma.