BI-RADS 4 = Suspicious abnormality – Biopsy should be considered
Because this is such a broad category, some radiologists may choose to further subdivide into:
4A: Finding with a low likelihood of being cancer (more than 2% but no more than 10%)
4B: Finding with an moderate likelihood of being cancer (more than 10% but no more than 50%)
4C: Finding with a high likelihood of being cancer (more than 50% but less than 95%), but not as high as Category 5
The report raised the possibility of fibroadenoma, so that this would tend more toward 4A.
Features on ultrasound that favor benignity include oval shape, parallel orientation, and circumscribed margins. Features on ultrasound that favor malignancy include irregular shape, not parallel orientation, and not circumscribed margins. In your case, parallel orientation is reassuring. Nevertheless, because nothing in medicine is ever 100% certain and sometimes bad things can mimic good things, biopsy is reasonable to be more definitive and alleviate your anxiety.
Hello and welcome to the forum. We appreciate your question but are sorry you are having this situation. It is important to remember that this rating given by the radiologist does not mean cancer but that they should investigate further. Our poster CHIN_C has given excellent and helpful information that hopefully helped guide you. Please let us know how your follow up went. We look forward to hearing an update.