Clinically Assessed Negative Axillary Lymph Nodes

The OMSLNB trial adopts a prospective, single-arm, non-inferiority, phase-II, open-label study design. Patients with unilateral invasive breast cancer （tumor ≤3cm） and assessed as cN0 will be eligible for inclusion, enrolled patients are required to complete 2 or more imaging tests including axillary ultrasound assessed as axillary lymph node negative, and other tests including MRI, PET-CT, \[18F\]-FDG PET-MRI, eligible patients will avoid axillary surgery but will undergo breast surgery, which is not limited to breast-conserving surgery (BCS). So as to decrease the edema of upper arm, and finally improve the quality of life of the patients.