In the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohorts, high stathmin mRNA expression was associated with high histological grade (both p < 0.001), tumour diameter > 20 mm (p = 0.019; validation cohort), and ER negativity both when assessing stathmin mRNA as a dichotomised variable (p < 0.001; cut-off median; Supplementary Table S3) and as a continuous variable (p ≤ 0.038). This evidence concerns the gene STMN1 and breast cancer.