Background Ultrasound (US) and contrast-enhanced ultrasound (CEUS) are commonly used to diagnose breast nodules. The diagnostic efficacy of ultrasound combined with ultrasonography varies with different sizes of breast nodules, but the diagnostic efficacy of ultrasonography for breast lesions < 1.0 cm is unknown.

Objective To analyze the diagnostic efficiency of conventional ultrasound combined with contrast-enhanced ultrasound in breast nodules of different sizes.

Methods Clinical data and ultrasound images of 847 patients who underwent routine ultrasound and CEUS with definite pathological findings in the Ultrasonography Department of the First Medical Center of Chinese PLA General Hospital from January 2021 to December 2022 were analyzed retrospectively. The nodules were divided into three groups according to their sizes: group 1 with size ≤ 1.0 cm, group 2 with size 1.0-2.0 cm, and group 3 with size > 2.0 cm. The CEUS characteristics of breast nodules in the three groups and the diagnostic efficacy of US combined with CEUS for breast nodules were compared.

Results The 847 patients were all female and ranged in age from 18 to 75 years with an average age of 45 years. The mean size of all lesions was 1.9 cm and ranged from 0.3 to 13.9 cm. There were 194 cases in the group 1 (148 benign and 46 malignant), 358 cases in the group 2 (220 benign and 138 malignant), and 295 cases in the group 3 (135 benign and 160 malignant). The characteristics of CEUS in malignant lesions were Centripetal enhancement, hyperenhancement, heterogeneous enhancement, ill-defined margin, irregular shape, enlarged enhancement scope and radial enhancement. The CEUS characteristics (enhancement uniformity, presence of filling defects and time to regression) of breast malignant lesions of different sizes differed, and the areas under the curve of the working characteristics of US combined CEUS for subjects with breast nodules in the three groups were 0.844, 0.932 and 0.928, respectively, with the area under the curve of the group of ≤ 1 cm being significantly lower than that of the other two groups (P < 0.005).

Conclusion CEUS features of breast lesions of different sizes are different. The diagnostic efficacy of conventional US combined with CEUS for breast nodules of different sizes varies, and the diagnostic efficacy is higher for lesions >1.0 cm.