Examining the same genes in CCND1-amplified vs. non-amplified luminal A tumours showed increased MKI67 and decreased PGR gene expression in amplified tumours (Fig. 3, see “MKI67” and “PGR”, P <  0.001 and P = 0.002 respectively), consistent with a more aggressive phenotype. This evidence concerns the gene MKI67 and neoplasm.