Abstract
BACKGROUND: Although T2-weighted imaging (T2WI) hypointensity, delayed enhancement washout pattern, interval growth, and new appearance of a focus have been associated with malignancy, the results are not consistent. PURPOSE: To investigate the malignancy rate and identify the clinical and imaging characteristics associated with malignancy among foci in breast MRI. STUDY TYPE: Meta-analysis. SUBJECTS: 32 articles with 2645 foci. FIELD STRENGTH/SEQUENCE: 1.5 T and 3.0 T. T1WI, T2WI, and DCE-MRI. ASSESSMENT: PubMed, Embase, Scopus, and Cochrane databases were searched for articles published from January 2013 to December 2023, using the search terms: "focus," "foci," "small mass," "size," "breast magnetic resonance imaging," and "breast MRI." Extracted data included the reference standard, number of benign/malignant foci, size criterion, BI-RADS categories, amount of fibroglandular tissue, background parenchymal enhancement, T2WI signal intensity, delayed enhancement pattern. STATISTICAL TESTS: Pooled data were analyzed using Revman 5.4 software. Between-study heterogeneity was investigated with I (2)-statistics. If I (2) < 50% (reflecting no substantial heterogeneity), a fixed effects model was used for analysis. If I (2) > 50%, random effects model analysis was used. For continuous variables, the standardized mean difference (SMD) and 95% confidence interval (CI) were used to represent the results. Malignancy rate of each study was transformed via the Freeman-Tukey Doublearcsine method. Odds ratios (OR) with 95% CIs were calculated for dichotomous variables. p values ≤ 0.05 were considered significant. RESULTS: The pooled malignancy rate of 2645 foci was 16% (95% CI: 13%-19%). There was a significant association between malignant foci and older age (OR = 5.82, 95% CI: 2.08-9.56), T2WI hypointensity (OR = 2.28, 95% CI: 1.19-4.35) and delayed enhancement washout pattern (OR = 2.78, 95% CI: 1.87-4.12). Hyperintense foci were significantly more likely to be benign (OR = 0.41, 95% CI: 0.21-0.79). DATA CONCLUSION: An enhancing focus with T2WI hypointensity and a washout pattern, especially in older patients, is significantly more likely to be malignant. Therefore, careful attention should be paid to it and could justify consideration of biopsy. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 3.