preferred_name: Documentation of reason(s) sentinel lymph node biopsy not performed (e.g., reasons could include but not limited to; non-invasive cancer, incidental discovery of breast cancer on prophylactic mastectomy, incidental discovery of breast cancer on reduction mammoplasty, pre-operative biopsy proven lymph node (ln) metastases, inflammatory carcinoma, stage 3 locally advanced cancer, recurrent invasive breast cancer, clinically node positive after neoadjuvant systemic therapy, patient refusal after informed consent, patient with significant age, comorbidities, or limited life expectancy and favorable tumor; adjuvant systemic therapy unlikely to change)