Characteristics and Pathologic Results of Foci on Breast Magnetic Resonance Imaging: A Systematic Review and Meta‐Analysis

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.