For particular breast cancer subtypes (classified by gene expression in KMplot; 41), we found that high MCAM expression significantly reduced overall survival in HER2+ (p < 0.01) and TNBC (p < 0.05), but not ER + tumours (Supplementary Figure S3A) and that high MCAM gene expression was significantly associated with a poor outcome when analysed for distant metastasis free survival in HER2+ tumours (p < 0.01), but not TNBC or ER + PR + tumours (Supplementary Figure S3B). This evidence concerns the gene ESR1 and breast carcinoma.