## 2 Materials & Methods
### Imaging Analysis  
For each patient, mammography, breast ultrasound and MRI were performed.  
Mammographic images were obtained in two standard planes [cranio-caudal (CC) and medio-lateral oblique (MLO)] using a full-field digital mammography system MAMOMAT Inspiration (Siemens Healthcare, Siemens, Erlangen, Germany). In 2019, a single MLO projection by means of a digital breast tomosynthesis system (DBT) was added. Breast sonography was performed using an ultrasound system (PHILIPS HD11 XE) equipped with a linear array L11-5 (5-12 MHz). The MR images were acquired on a 1.5 T system (Siemens Avanto, version Syngo MR B19 and Siemens Aera, version syngo MR E11) using dedicated 4-channel phased array breast coils. The patients were examined in the prone position. Images were acquired using the following pulse sequences on axial planes: T2 short tau inversion recovery, STIR (repetition time, 6210 ms; echo time, 41 ms; slice thickness, 3 mm; field of view, 400 \(\times\) 362 mm; matrix, 384 \(\times\) 313 pixels; duration, 2:49 min), T1 flash 3D (repetition time, 7.59 ms; echo time, 4.76 ms; slice thickness, 1.5 mm; field of view, 400 \(\times\) 334 mm; matrix, 416 \(\times\) 313 pixels; duration, 1:06 min), T1 flash 3D spectral adiabatic inversion recovery, and SPAIR (repetition time, 4.96 ms; echo time, 2.39 ms; slice thickness, 1.5 mm; field of view, 400 \(\times\) 350 mm; matrix, 384 \(\times\) 319 pixels; duration, 0:58 min), obtained before and five times after an intravenous bolus injection of a 0.15 mL/kg body weight dose of paramagnetic contrast medium (gadoteric acid 0.5 mmol/mL) at a rate of 3 mL/s. The imaging protocol included diffusion images with a b-value of 500-1000 s/mm\({}^{2}\) (repetition time, 7400 ms; echo time, 66 ms; slice thickness, 3 mm; field of view, 380 \(\times\) 213 mm; matrix, 164 \(\times\) 92 pixels; duration, 3:42 min) and apparent diffusion coefficient (ADC) maps. In addition, T1 flash 3D on sagittal planes was performed (repetition time, 4.89 ms; echo time,1.54 ms; slice thickness, 2 mm; field of view, 280 \(\times\) 236 mm; matrix, 480 \(\times\) 365 pixels; duration, 1:51 min). All exams were analyzed by two radiologists experienced in interpreting breast imaging.  
Mammographic, sonographic and MRI studies were evaluated according to the 5 th edition of BI-RADS lexicon. In particular, in the mammography analysis we evaluated: the presence of a mass and its characteristics such as shape (round, oval or irregular), dimensions (<1 cm and \(\geq\)1 cm) and margins (regular or irregular), the presence of micro-calcifications and their morphology and distribution, and the presence of any architectural distortion. At the ultrasound exam, we reported the presence of a mass and its features (i.e., shape, dimensions and margins) and echo pattern (anechoic, hyperechoic, complex cystic and solid, hypoechoic, isoechoic or heterogeneous).  
The features reported in MRI were the \"background parenchymal enhancement\" (minimal, mild, moderate or marked) and its distribution (symmetric or asymmetric), the presence of a mass enhancement (with its shape, dimensions, margins and pattern of enhancement according to intensity/time curves of type I, II and III) or a non-mass enhancement (focal, linear, segmental, regional, multiple regions or diffuse).  
All these radiological features were reported for each patient and a correlation between these characteristics, the type of genetic mutation, the type of B3 lesions identified at breast biopsy (both core needle biopsy and VAB) and the definitive histological diagnosis was performed.