Serial Ultrasound Findings After Microwave Ablation for Benign Breast Lesions

Post-ablation ultrasound findings after microwave ablation (MWA) for benign breast lesions (BBLs) can mimic malignancy, leading to diagnostic confusion. This study aimed to characterize the longitudinal evolution of sonographic features after MWA and identify factors associated with malignant-like echogenic patterns (MEPs).

This retrospective study included female patients with BBLs who underwent ultrasound-guided percutaneous MWA between August 2015 and October 2022. Ultrasound features were documented at baseline and at 1-6 months, 1 year, 2 years, and 3 years post-ablation. Independent predictors of MEPs were identified using multivariable logistic regression with Firth's penalized likelihood, and an XGBoost model was constructed to predict MEPs and evaluate feature importance.

A total of 314 patients (mean age: 38 ± 12 years) with 549 BBLs (1.5 cm (IQR, 0.6-4.0 cm)) were included. At 1-6 months, 85.8% of lesions showed benign evolution patterns (BEPs), 12.0% presented as concentric circular echogenicity (CCE) lesions, and 2.2% as nodular uneven low echogenicity (NULE, classified as MEP) lesions. By 3 years, 75.8% of BEP lesions progressed to complete absorption, while 54.5% of CCE lesions and 83.3% of NULE lesions persisted as MEPs. Independent predictors of MEPs included NULE at 1-6 months, CCE, adjacency to the pectoralis muscle, fibroglandular background, Doppler flow, irregular shape, and heterogeneous echogenicity.

Although MEPs may mimic malignancy, histology confirmed their benign nature. Recognizing these evolving sonographic changes can improve diagnostic confidence and reduce unnecessary interventions.