BACKGROUND/AIM: Sentinel lymph node (SLN) procedures have gained popularity in early breast cancer thanks to the reduction of surgical side-effects. The standard SLN mapping procedure uses Tc-nanocolloid human serum albumin with/without blue dye; limitations include logistical challenges and adverse reactions. Recently, contrast-enhanced ultrasound (CEUS) using sulfur hexafluoride has emerged as a promising technique for SLN mapping. Our study aimed to compare the CEUS technique with the standard isotope method. MATERIALS AND METHODS: AX-CES, a prospective, monocentric, single-arm phase-3 study was designed (EudraCT: 2020-000393-20). Inclusion criteria were histologically diagnosed early breast cancer eligible for upfront surgery and SLN resection, bodyweight 40-85 kg, and no prior history of ipsilateral surgery or radiotherapy. All patients underwent CEUS prior to surgery and blue dye injection was performed in areas with contrast accumulation. After the experimental procedure, all patients underwent the standard mapping procedure and SLN frozen section assessment was performed. Data on the success rate, systemic reactions, mean procedure time, CEUS appearance, SLN number, and concordance with standard mapping procedure were collected. RESULTS: Among 16 cases, a median of two SLNs were identified during CEUS. In all cases, at least one SLN was identified by CEUS (100%). In six cases, SLNs were classified during CEUS as abnormal, which was confirmed by definitive staining in four cases. After the standard mapping technique, in 15 out of the 16 cases (87.50%), at least one SLN from the standard mapping procedure was marked with blue dye in the CEUS procedure. In our series, sensitivity and specificity of SLN detection by CEUS were 75% and 100%, respectively. CONCLUSION: CEUS is a safe and manageable intraoperative procedure. When compared with standard techniques, US appearance during CEUS may provide additional information when associated with histological assessment.