ESR1 and neoplasm: Additionally, the resection-associated recurrence following primary tumour resection displays an apparently similar time-course for every ER class, suggesting caution in the interpretation of the clinical meaning of the two main subtypes of breast cancer identified by epidemiological features linked to ER expression [9] and gene expression profiling (luminal A and basal-like, phenotypically referred as ERP and ERN, respectively) [10] as well as the distinct gene expression patterns associated with ER status [11].