From the Guidelines
A BI-RADS 4 classification indicates a suspicious abnormality with a moderate risk of malignancy, requiring a biopsy for definitive diagnosis. The next step is to undergo a tissue biopsy, typically a core needle biopsy, which removes small samples of breast tissue from the suspicious area. This procedure is usually performed under local anesthesia and may be guided by ultrasound, stereotactic (mammogram-guided), or MRI techniques depending on how the abnormality is best visualized 1. After the biopsy, the tissue samples will be examined by a pathologist to determine if cancer cells are present. While awaiting results, which typically take 3-7 days, patients should follow up with their referring physician or breast specialist to discuss the findings. It's essential to understand that BI-RADS 4 is further subdivided into categories 4A (low suspicion), 4B (moderate suspicion), and 4C (high suspicion), which helps physicians communicate the level of concern. Though a BI-RADS 4 finding is concerning enough to warrant biopsy, approximately 70-80% of these lesions turn out to be benign, so patients should not assume they have cancer while awaiting results.
Some key points to consider:
- The BI-RADS 4 category has a wide range of probability of malignancy, but it is greater than that for category 3 and less than that for category 5 1.
- A tissue biopsy is recommended for BI-RADS category 4 or 5 (suspicious or highly suggestive of malignancy) 1.
- The NCCN Panel recommends a tissue biopsy if diagnostic imaging findings or clinical findings are suspicious (BI-RADS 4) or highly suggestive of malignancy (BI-RADS 5) 1.
- Core needle biopsy is the preferred method for biopsy in cases with BI-RADS category 4-5 1.
Overall, a BI-RADS 4 classification requires prompt attention and further evaluation to determine the presence of malignancy, and a biopsy is the next step in management.
From the Research
BI-RADS-4 Classification
A BI-RADS-4 classification indicates a suspicious abnormality that does not fulfill the typical criteria for malignancy but is suspicious enough to warrant a recommendation for biopsy 2. This category covers a wide range of probability of malignancy, from >2 to <95%.
Next Steps
The next steps for a BI-RADS-4 classification typically involve a biopsy to determine the nature of the abnormality. MRI can aid in the noninvasive differentiation of benign and malignant lesions and may help avoid unnecessary breast biopsies 2.
Subcategorization of BI-RADS-4 Lesions
BI-RADS-4 lesions can be subcategorized into 4A (low suspicion for malignancy), 4B (intermediate suspicion of malignancy), and 4C (moderate concern, but not classic for malignancy) 3, 4. The subcategorization is important as it helps in understanding the level of concern for carcinoma and guides further management. For example, a study found that 70% of BI-RADS 4C category lesions were ductal carcinoma in situ (DCIS), while only 21% of BI-RADS 4B and 10% of BI-RADS 4A were DCIS 3.
Sonographic Features
Sonographic features of BI-RADS-4 lesions can be evaluated using the BI-RADS US lexicon 4, 5. However, the sonographic features are not sufficient to discriminate between malignant and benign lesions, and biopsy is often required. A study found that typical signs of malignancy included irregular shape, spiculated margin, and nonparallel orientation, while typical signs of benign lesions included oval shape, circumscribed margin, parallel orientation, and abrupt interface 4.
Reducing Unnecessary Biopsies
Recent studies have explored the use of deep transfer learning methods to reduce the number of unnecessary biopsies for mammographic BI-RADS 4 lesions 6. These methods have shown promise in improving the accuracy of lesion classification and reducing the number of unnecessary biopsies. For example, a study found that a deep transfer learning model achieved a precision of 0.90, recall rate of 0.90, F1 score of 0.90, and area under the receiver operating characteristic curve of 0.86 for category 4 lesions 6.