Background <p>Breast cancer is the most frequent disease diagnosed worldwide and the primary cause of cancer death for women. Prognosis and treatment choices for patients with breast cancer depend on the precise detection of axillary lymph node (ALN) involvement. We aimed to compare the pre-operative axillary ultrasound findings and the post-operative pathological results, which resulted either from sentinel lymph node biopsy (SLNB) or axillary lymph node dissection (ALND) in breast cancer patients.</p> Results <p>Sixty-nine females were included in this retrospective study. All patients were subjected to breast surgeries, including axillary lymph nodes removal techniques, either ALND or SLNB; 35 out of the 69 patients underwent ALND, while 34 patients underwent SLNB.</p> <p>Sono-mammography was performed on all patients pre-operatively, with a dedicated assessment of the axillary lymph nodes. The morphologic criteria of the examined lymph nodes were carefully analyzed and classified according to guidelines into nonspecific, indeterminate, and pathological categories. Then, the overall diagnostic performance of axillary US was evaluated, and the results were strictly compared with the post-operative pathological results.</p> <p>In the whole population of the study, we reported high sensitivity (73.8%), specificity (70%), and accuracy (72.4%) of pre-operative axillary ultrasound, with a differential predilection toward sensitivity (96.4%) in the ALND group of patients and specificity (75%) in the SLNB group of patients.</p> Conclusions <p>In pathological axillary lymph nodes diagnosed by axillary ultrasound, ALND would be the ideal procedure in order to avoid the post-operative recurrence and further metastasis, while in non-specific axillary lymph nodes by axillary ultrasound, SLNB would be the ideal technique to avoid unnecessary complications of ALND, such as lymphedema, seroma, infection, and numbness.</p>