We hypothesized from these results that the axillary lymph node metastasis process is predominantly correlated to intrinsic biological properties in the ER negative HER2 negative breast cancer subgroup whereas stochastic events, tumour size, growth rate and lympho-vascular invasion are the main determinants in the ER positive or HER2 positive breast cancer subgroups. The gene discussed is ESR1; the disease is breast carcinoma.