Prevalence and outcomes of nonmass lesions detected on screening breast ultrasound based on ultrasound features.

Purpose: To determine how often non-mass lesions are seen in screening breast ultrasounds, and analyze their ultrasound features according to the ultrasound lexicon to find features suggestive of malignant non-mass lesions.

Methods: This study is a single center retrospective study for nonmass lesions on screening breast ultrasound. Among 21,604 patients who underwent screening breast US, there were 279 patients with nonmass lesions. Of these lesions, 242 lesions were included for analysis. To distinguish between benign and malignant nonmass lesions, univariate analysis was performed on size, echogenicity, distribution, orientation, and associated ultrasound features. Additionally, Fisher's exact test was performed for mammographic density and abnormalities.

Results: 279 patients with nonmass lesions were included (mean age 53.7 ± 9.7 years, all women). The incidence of nonmass lesions on screening breast ultrasound was 1.29% with positive predictive value of 5.78%. The most common malignant nonmass lesion was ductal carcinoma in situ. Nonparallel orientation (p = 0.002), echogenic rim (p = 0.005), architectural distortion (p = 0.0004), posterior shadowing (p = 0.007), vascularity (p < 0.001), and calcifications (p < 0.001) were indicators of malignant lesions. Additionally, mammographic abnormalities were significantly associated with malignant lesions (p < 0.001).

Conclusion: The incidence of nonmass lesions on screening breast ultrasound was 1.29%, with a positive predictive value of 5.78%. Mammographic abnormalities, nonparallel orientation, architectural distortion, posterior shadowing, vascularity, and calcifications were associated with malignant nonmass lesions.