ESR1 and metastatic malignant neoplasm in the lymph nodes: We identified significant differences between these 4 categories in terms of histological type (14% were lobular carcinoma in ER positive HER2 negatives subgroup, 13% were “other type i.e medullary carcinoma” in ER negative HER2 negative subgroup, p = 9e–05), lympho-vascular space involvement (34%, 36%, 47%, 60%, p = 0.02), multifocality (19%, 0%, 31%, 29%, p = 0.02), and percentage of non-sentinel axillary lymph node metastasis (27%, 9%, 41%, 39%, p = 0.03).