Case 37 Answer
This is a lobulated spiculated mass, and is highly suggestive of malignancy based on the mammogram and tissue sampling is indicated. An ultrasound will not change this assessment. However, an ultrasound will help establish size and determine how to proceed with needle biopsy. Therefore, BI-RADS 0 is technically the best answer since additional imaging is being recommended.
In this case, ultrasound-guided core biopsy yielded infiltrating ductal carcinoma, which was localized again with ultrasound-guidance.