Of 14 923 female patients who underwent curative surgery for ER+/ERBB2− invasive breast cancer, a total of 2295 were included in the study (mean [SD] age, 49.8 [9.3] years); among them, 1948 (84.9%) belonged to the low genomic risk group and 1425 (62.1%) had low Ki-67 expression. This evidence concerns the gene MKI67 and invasive breast carcinoma.