Objective To investigate the predictive value of contrast-enhanced ultrasound combined with serological markers for axillary lymph node metastasis in breast cancer patients under 40 years

so as to provide a reference for clinical diagnosis. Methods A total of 157 patients with breast cancer who received surgical treatment in the Dalian No.3 People’s Hospital from January 2017 to January 2021 were selected as the study subjects. They were assigned to the age <40 years group and age ≥40 years group according to age. Patients aged <40 years were assigned to the metastatic and non-metastatic groups according to the presence or absence of lymph node metastasis. Relevant clinical data of patients were collected

including contrast-enhanced ultrasound parameters and tissue polypeptide specific antigen（TPS）

thymidine kinase 1（TK1）

and vascular endothelial growth factor（VEGF） levels. Multivariate logistic regression analysis was employed to analyze the correlation between the above parameters and axillary lymph node metastasis. Results Significant differences in angiographic perfusion defect signs and peak intensity were observed among different aye groups（P<0.05）. There were significant differences in lymph node rim enhancement

acoustic halo around lymph nodes

lymph node perfusion order

lymph node diameter enlargement

lymph node blood flow grade

lymph node enhancement pattern

lymph node aspect ratio

maximum cortical thickness of lymph nodes

and relative area under the curve of the primary tumor between the metastatic group and the non-metastatic group（P<0.05）. Significant differences in TPS and TK1 levels were also observed between the metastatic group and the non-metastatic group（P<0.05）. Logistic regression analysis showed that lymph node enhancement

lymph node enlargement

maximum cortical thickness of lymph nodes

and TPS and TK1 levels were all independent factors affecting the diagnosis of axillary lymph node metastasis in breast cancer patients under 40 years（P <0.05）. Conclusion Compared with patients over 40 years

breast cancer patients under 40 years have higher peak values in contrast-enhanced ultrasonography signs and are also more likely to develop perfusion defects. Meanwhile

lymph node enhancement

lymph node enlargement

maximum cortical thickness of lymph nodes

and TPS and TK1 levels in contrast-enhanced ultrasound signs can predict whether axillary lymph node metastasis occurs in breast cancer patients and have guiding significance for clinical diagnosis and treatment.