To assess the application value of contrast-enhanced ultrasound in the diagnosis and biopsy of American College of Radiology breast imaging reporting and data system (BI-RADS) category 4a breast nodules.

A retrospective analysis was performed on the imaging data and coarse needle biopsy or surgical pathological results of 126 patients with BI-RADS category 4a breast nodules who received contrast-enhanced ultrasound examination at the First People's Hospital of Jiashan County, Zhejiang Province from January 2020 to February 2023. Single factor analysis and multivariate regression analysis were conducted to identify independent risk factors for breast nodule malignancy. Using pathological results as the gold standard, receiver operating characteristic (ROC) curve analysis was performed to calculate the sensitivity, specificity, and accuracy of contrast-enhanced ultrasound for diagnosing benign and malignant nodules, and analyze the diagnostic efficacy of contrast-enhanced ultrasound for BI-RADS category 4a breast nodules. The puncture biopsy rate, malignant nodule detection rate, and missed detection rate of all breast BI-RADS 4A nodules were compared with those of nodules that tended to be malignant after contrast-enhanced ultrasound.

Among the 126 cases of breast BI-RADS 4A nodules, there were 97 cases of pathologically benign nodules and 29 cases of pathological malignant nodules. The results of multivariate logistic regression analysis showed that the expansion of lesion size after enhancement (odds ratio [OR]=10.800, P=0.048) and the "crab foot" sign or nutrient vessels (OR=6.909, P=0.027) were independent risk factors for breast nodule malignancy. The area under the ROC curve of contrast-enhanced ultrasound in the diagnosis of benign and malignant BI-RADS category 4a breast nodules was 0.792, and the sensitivity, specificity, and accuracy were 86.2%, 72.2%, and 75.4%, respectively. After contrast-enhanced ultrasound examination, the biopsy rate for the 126 BI-RADS category 4a breast nodules decreased from 100.0% before contrast to 41.2% (χ²=104.76, P<0.001), and the detection rate of malignant nodules increased from 23.0% to 48.1% (χ²=10.93, P=0.001), with a missed detection rate of only 3.1% (χ²=1.759, P=0.815).

Contrast-enhanced ultrasound has high efficacy in the differential diagnosis of benign and malignant BI-RADS category 4a breast nodules, with the potential to reduce unnecessary biopsy of BI-RADS 4A nodules and improve the detection rate of malignant nodules.