**3.1 Reporting system**

The Breast Imaging Reporting and Data System® (BI-RADS®) is a management system developed for imaging that contains: (1) a lexicon of descriptors, i.e., a dictionary of specific imaging features; (2) a standardized reporting structureincluding final assessment categories with accompanying recommendations; (3) a framework for data collection and auditing. This system aids communication and comprehension of imaging findings by all members of the multidisciplinary breast care team: surgeons, pathologists, oncologists, radiologists, and other health care providers. BI-RADS final assessment categories and their recommendations have become the standard by which physicians determine breast care, allowing uniform drafting of reports, facilitating the research, and performance evaluation [9].

These categories, currently are as follows [10]:


Similarly, in the UK, the Royal College of Radiologists Breast Group (RCRBG) [11] has developed a five-point scoring system to classify breast images, using a similar rationale to the American College of Radiologists' development of the BI-RADS®. However, this classification does not specify the probable cancer risk of each category. This five-point system is Normal (category 1)- there are no significant imaging findings. Benign findings (category 2)- the benign imaging findings are not indicated for further investigation. Indeterminate / probably benign (category 3)- low risk of malignancy, and further investigation through needle biopsy is indicated. Findings suspicious of malignancy (category 4)- show a moderate risk of malignancy, so further investigation is indicated through a needle biopsy. Highly suspicious findings of malignancy (category 5)- high risk of malignancy; further investigation is indicated through a needle biopsy.

### **3.2 Imaging quality**

The US is a highly operator-dependent technique due to a lack of repetitiveness and a strong reliance on specialists' abilities and judgment to capture the right image to be documented in the report. Although the ACRIN 6666 trial has proposed a model, no standard US acquisition technique exists yet [12]. A specialist with competence and experience should perform breast ultrasound [13, 14], correlating clinical signs or symptoms, mammographic studies, and other breast imaging. If the ultrasound has been performed previously, the current examination should be compared with a previous ultrasound, as appropriate.

### **3.3 Setting**

The correct application of the vocabulary depends on the quality of the ultrasound equipment, ultrasound technique, and an adequate compression of the breast anatomy. Breast ultrasound should be performed with high-resolution linear array transducers from 7.5–8 (at least) to 15–18 MHz. Higher frequency is recommended for less depth penetration (superficial details or small breasts). Lower frequency should be used for deeper areas or very large breasts (4 to 8 MHz) [5]. An acoustic stand-off pad is useful for superficial images. It is critical to document and capture appropriate imaging for actionable cases by optimizing focal zone selections, gain settings, and view fields. When a potential finding is located, turn the transducer to assess if it persists and better characterize it. A wide-band linear matrix transducer offers better resolution by focusing on the short axis.

### **3.4 Positioning**

The patient should be lying in the supine position placed with the chest undressed. There are two breast survey patient positions: a medial position with the ipsilateral arm overhead or with arms flexed behind the head to flatten the breast, and an oblique position with a wedge supporting the back for scanning the lateral part of the breast and the axilla. Scan techniques should allow systematic exploration of the entire breast, whether grid scanning or radial scanning patterns.

### **3.5 Labeling**

Images should be labeled as right or left breast and should be reported the transducer orientation. The localization of the findings is described by quadrant -upper external, lower external, lower internal, upper internal- and retroareolar region; or according to the clock-wise position (distance from the nipple). Distance from the nipple to the lesion should not be measured from the areola's edge since the areolar width is variable [5]. A large lesion can be captured in a single image by Panoramic Imaging (Extended Field of View –FOV-) and traced the lesion back to the nipple for an accurate distance reporting.

### **3.6 Measurements**

All lesions are measured in three dimensions, including length, width, and height unless shadowing disguises the accurate height measurement. Dimensions must register with the greatest millimeter or centimeter accuracy. The first measurement represents the longest axis. The following measurement is perpendicular to the long axis, and the last measurement is from an orthogonal projection to the first image (representing a different plane from the former two images). It is necessary to capture two sets of lesion images (one with calipers and one without) [6, 10].

Solid masses diagnosed as benign pathology may safely have periodic surveillance if the volume growth rate is less than 16% per month in women under 50 years and less than 13% per month in women 50 years or older. An acceptable mean change for three dimensions during a six-month interval is 20% for all ages [15].
