[Retrospective analysis of BI-RADS 4 and 5 lesions additionally detected by breast MRI].

To establish a newly-designed scoring system for breast imaging-reporting and data system (BI-RADS) 4 and 5 breast lesions only visible on MRI, and to examine their clinical pathway of biopsy. The BI-RADS 4 and 5 breast lesions only visible on MRI but not suspected on mammograms or ultrasound between June 2007 and December 2021 at Beijing Hospital were evaluated retrospectively. A total of 209 lesions from 184 patients were finally included. All patients were female, aged (50±11) years (range: 27 to 76 years). All lesions were confirmed by pathology and divided into malignancy and non-malignancy. The lesions were divided into mass and non-mass type using BI-RADS. The receiver operator characteristic (ROC) curve was used to evaluate the diagnostic performance of the new scoring system. Four types of pathology-obtaining pathway were used: biopsy guided by second-look ultrasound, local excision guided by lesion position information on MRI, intraductal lesion excision guided by methylene blue stain and mastectomy. The data between mass and non-mass lesions were compared by Mann-Whitney test, test or Fisher exact test,respectively. There were 124 malignant and 85 non-malignant lesions, while 100 mass and 109 non-mass lessions. The sizes between mass and non-mass lesions showed significant difference((IQR)) (7.0 (3.0) mm 25.0 (25.0) mm, =568.000, <0.01) and their BI-RADS diagnostic accuracy had no significant difference (53.0% (53/100) 65.1% (71/109), =3.184, =0.074). The areas under ROC curve of the new scoring system for evaluating mass and non-mass were 0.841 and 0.802, respectively. When taking Score 3 as threshold, it can potentially avoid 14.0% (14/100) and 4.6% (5/109) of biopsies in mass and non-mass, respectively. As to pathway of obtaining pathology, second-look ultrasound succeeded more easily in mass than non-mass (41.0% (41/100) .26.6% (29/109), =4.851, =0.028). More MRI-guided local excisions were performed in non-mass than mass (52.3% (57/109) 34.0% (34/100), =7.100, =0.008). For suspicious breast lesions detected by MRI but not suspected on X-ray or ultrasound, the new scoring system can further increase diagnostic accuracy. The second-look ultrasound plays an important role for obtaining pathology, especially for mass-type lesion.