• mri-only lesions
• mri-guided vacuum-assisted breast biopsy
• mr imaging
• breast cancer

Magnetic resonance imaging (MRI) of the breast is the most sensitive method for the detection of breast cancer (86-100%). Although its high sensitivity, the reported specificity of breast MRI ranges from 37 to 78%, which depends greatly on the indications. Even if the EUSOMA guide-line indications and technical quality criteria are followed however, there is considerable overlap in the MRI appearance of benign and malignant lesions. A significant proportion of the suspicious lesions detected on breast MRI (RM 4, RM5) are not identified on MRI-directed ultrasonography (2nd look US) and are occult on mammography (2nd look DBT).In case of a suspicious MRI-only lesion, histological verification with MRI guided VABB is mandatory. Within this context, the aim of the present study is to assess the effectiveness of MRI-guided 9 Gauge (G) vacuum-assisted breast biopsies (VABB) performed at our institution, to examine the relationship between lesion characteristics and histopathologic results and overview the follow-up results of benign lesions. We retrospectively reviewed the radiological records of 74 lesions of 72 women aged from 27 to 78 years (mean age 52 years) consecutively referred to our department for MRI-guided VABB between July 2018 and November 2020. Lesions included in the study were MRI-detected lesions described according to the Breast Imaging and Reporting Data System (BI-RADS) Breast MRI Lexicon and classified as BI-RADS category 4 or 5 that were occult both on mammography and ultrasound. In eight cases procedures could not be performed because of a lack of visualization of the biopsy target on preparation sequences of MRI biopsy session (7 patients) and for the detected correspondence between the target of biopsy and the site of a previous stereotactic vacuum-assisted biopsy (1 patient), so these lesions were excluded from the study. Finally, 66 lesions of remaining 64 patients, constituted the study group. Patients in this cohort were evaluated with breast MRI due to the following indications: preoperative staging of newly diagnosed breast cancer (38%), problem solving modality (34%), screening for high-risk women (8%), B3 lesions (7%), scar tissue study (7%), nipple discharge (5%), CUP syndrome (1%). Patients were advised about the procedure, post-intervention follow-up, and possible complications. All participating patients gave written informed consent. The MRI-guided vacuum-assisted biopsies were performed by one radiologist specializing in diagnostic and interventional breast imaging. A 1.5 T MRI scanner (Optima 450 W; GE Healthcare) was used for the procedures. Patients were placed in the prone position, and the images were acquired with a dedicated 8-channel coil, which provides lateral and medial access to the breast. A median of 12 specimens per lesion was obtained (range8-24). Specimens were fixed in neutral buffered formalin. The tissue sampled was entirely embedded and examined by pathologists with experience in breast pathology. For all the patients, results of MRI-guided biopsies were reviewed during a multidisciplinary session to assess radio-pathological concordance.When histological findings could not explain the MRI findings, surgical biopsy was recommended. In cases of benign histological findings concordant with the MRI pattern, MRI follow-up was recommended at 4–6 months, and then 1 year later. Data collected included: type of biopsy access, MRI lesion size and type, MRI-guided histological findings, follow-up, final surgical histology and complications. Data were entered into a computerized spreadsheet (Microsoft Excel) for analysis. Among a total of 74 cases referred for MRI-guided vacuum-assisted biopsy, the procedure was deleted in eight (10,8 %). Therefore, MRI-guided VAB was performed for 66 lesions in 65 women between 27 and 78 years of age (mean age, 51.5 years). The median procedural time was 40 min (range.30-60 min). Overall, 42 of 66 lesions were benign (B2, 64%), 12 were probably benign (B3, 18%) and 12 were malignant (B5, 18%). Fifteen of 66 lesions (23%) were masses, 19 (29%) were foci, and the remaining 32 (48%) were NME lesions. Segmental (29%), regional (33%) and clustered ring (50%) non-mass-like enhancement pattern were found to be more related with malignancy. Our data suggest that MRI-guided VAB represents an accurate tool for the histological diagnosis of lesions visible only at MRI. In our sample the overall malignancy rate was 18%. However, because this was a preliminary experience, studies involving the correlation with larger surgical data and longer follow-up are needed in order to improve the assessment of these results.