Ultrasonic contrast enhancement and detection of sentinel lymph nodes in patients with breast cancer: A prospective single-center study

Background. For a personalized approach and the choice of treatment for patients with breast cancer (BC), the correct staging of the tumor process, including the assessment of the status of regional lymph nodes (LN), remains an important task. After the introduction of the sentinel lymph node (SLN) concept into clinical practice, it became possible to remove only one LN through which lymph drainage from the mammary gland occurs and to assess its status during urgent and planned histological examination. At the current stage of oncology and radiological diagnostic method development, SLNs are primarily detected using isotopic and fluorescent drugs. The most promising areas include the use of the SLN detection technique with an ultrasonic sulfur hexafluoride contrast medium. This technique is being gradually integrated into clinical practice due to its high diagnostic value; however, it is necessary to detail its diagnostic capabilities, develop utilization algorithms, and establish specific indications for its use.

Aim. To study the possibilities of using an ultrasound contrast medium, sulfur hexafluoride, in the SLN detection, to identify the main enhancement patterns, and to determine the contrast uptake features of SLN with metastatic lesions in patients with BC.

Materials and methods. The prospective study was conducted at the Department of Breast Pathology and the Imaging Department of the Kulakov National Medical Research Center for Obstetrics, Gynecology, and Perinatology from May to October 2024. This part of the study included 144 patients (91 with stage I surgery and 53 after neoadjuvant chemotherapy) with primary resectable stage I-IIIa BC (cT_1-3N_0-1M₀), the average age was 52.4 years. The detection technique using ultrasonic imaging was performed with paraareolar and intradermal injections of the sulfur hexafluoride contrast medium on the affected side. Imaging with contrast enhancement was performed on the Mindray Resona 7 Diagnostic Ultrasound System (PRC) with contrast function.

Results. The study detected SLN in 137 cases (out of 144), resulting in a detection rate of 95.1%. In most cases, 1 SLN was detected; in 24 (17.5%) patients, 2 SLNs were detected. In 7 (4.9%) cases, no SLN was detected (false negative results). There were 6 types (patterns) of contrast medium uptake: Type I (homogeneous, intensive), Type II (homogeneous, low-intensity), Type III (heterogeneous distribution of ultrasonic contrast medium with perfusion defects of <50% of the LN volume), Type IV (heterogeneous contrast enhancement with perfusion defects of >50% of the LN volume), Type V (annular), Type VI (contrast-enhanced lymphatic duct, without ultrasonic contrast medium uptake in the LN; LN structures are visualized in B mode). The most common patterns in metastatic disease were IV, V, and VI. Patterns I, II, and III were typical for LN with no signs of metastasis.

Conclusion. Detection of SLN using ultrasound contrast-enhancement technique is an easily available and reproducible method in clinical practice in patients with BC, and the assessment of the intensity of the accumulation and distribution of contrast medium with ranking by selected patterns may indicate the presence of metastases in the LN.