Analysis of the subclasses by clinicopathological features revealed that HR+/HER2-low and HR+/HER2-zero breast cancers had similar characteristics: 59–60% were stage 1, 63% had N0 nodal status, 50–51% were grade 2 tumours, and 55% of tumours measured 20mm or smaller (Table 12). This evidence concerns the gene ERBB2 and breast cancer.