BI-RADS stands for the Breast Imaging-Reporting and Data System. Along with breast density, it is the only other mandated requirement to appear in your breast report. Your BI-RADS score determines your next course of action. Structured data reporting and collection began with mammography. Just as Apple has the iEverything, the American College of Radiology (ACR) as the I-RADS system. Now, there is liver (LI-RADS), thyroid (TI-RADS), and prostate (PI-RADS), just to name a few, with the goal being to help improve research.
The ACR is on its 5th edition to the BI-RADS atlas. The atlas provides a lexicon and standardized nomenclature to facilitate communication between radiologists, as well as breast surgeons and oncologists/cancer doctors. This means everyone should be using the same words to describe particular features of the breasts and possible lesions. For example, a mass by definition has convex margins (umbrella upright) and is seen on two views. A focal asymmetry has concave margins (umbrella upside down) and is also seen on two views. An asymmetric density is seen only on a single view. Of course there are dedicated words to describe just about anything you can visualize in breast imaging.
So what does my BI-RADS mean?
Category 0: Incomplete – Need Additional Imaging Evaluation and/or Prior Mammograms for Comparison. Recall for additional imaging and/or comparison with prior examination(s). This means we either need to get prior mammograms, since we do not have your priors for comparison, or we see something on your screening exam that causes us to send you a callback letter.
Category 1: Negative – Routine mammography screening. You scored! Have a great day and come back next year for your ANNUAL mammogram.
Category 2: Benign – Routine mammography screening. A radiologist could make you a 2 for essentially anything. The point is you do not have any mammographic findings concerning for cancer. You too should have a great day and be sure to return next year!
Category 3: Probably Benign Short-interval (6-month) follow-up or continued surveillance mammography. The ACR suggests > 0% but ≤ 2% likelihood of malignancy. I rarely call a 3 and if so, it is usually for a fibroadenoma on ultrasound (common benign breast lesion) often first detected in women in their 20-30s. I will also call a 3 for clustered calcifications that I think are benign, but it is either the persons first exam or there was more than a year’s gap between mammograms when detected. Basically, I am almost 100% certain it is benign/non-cancerous and does not need to be biopsied.
Category 4: Suspicious Category 4A: > 2% to ≤ 10% likelihood of malignancy Category 4B: > 10% to ≤ 50% likelihood of malignancy Category 4C: > 50% to < 95% likelihood of malignancy. So we just took a 7 point classification system and made it 9 classes. I, like many radiologists, feel this is unnecessary. I classify something a 4 if I think it has a reasonable chance of being a cancer. I don’t break it down into A, B, and C. Nationwide, about 4/10 lesions biopsied are cancers. As a group, radiologists are more sensitive and less specific. That is, we are trained to diagnose cancers early and are willing to biopsy more women to catch smaller or more questionable lesions.
Category 5: Highly Suggestive of Malignancy Tissue diagnosis ≥ 95% likelihood of malignancy. A radiologist who helped me during training told me that calling a 5 means you are absolutely certain there is a cancer and you are willing to stake your reputation on it. Wow, that’s serious! I use a BI-RADS 5 differently. To me it means that when I do a biopsy and stick a needle into that breast taking pieces of the lesion, under no circumstances will I accept a negative biopsy result from the pathologist. Talk about serious!! I have called 5’s in my career and have had some biopsies come back NO CANCER. They are discordant. That is to say that on imaging it looks so much like a cancer that I am absolutely shocked the pathologist didn’t find any cancer under the microscope. So a phone call is made to discuss the case my fellow pathologists. Not every piece of tissue that is taken is reviewed microscopically. I have had cancers found on a second review before (happens on imaging too!). Regardless, a surgeon needs to go in there and cut that out. As we say in medicine, it belongs in the bucket! Over the past decade I have personally had three cases where the pathology was discordant with the imaging findings and surgeons excised cancer based upon my recommendations. It does happen.
Category 6: Known Biopsy-Proven Malignancy Surgical excision when clinically appropriate. BI-RADS 6 are usually only seen with biopsy proven cancers who are getting MRI for presurgical planning or imaging assessment for response to neo-adjuvent chemotherapy, which is chemotherapy given to shrink the tumor before they cut it out.
I read a bit over 3,000 mammograms a year, not a small number. Our practice has been using 3D tomosynthesis mammography for almost five years now with 2D digital mammography for well over a decade. We are available for stereotactic guided biopsies every Tuesday and Thursday when scheduled. We perform US guided biopsies on weekdays, as we are an outpatient facility. MR guided biopsies are only performed when the lesion is not visualized on mammogram or ultrasound.
I hope that gives you a sense of what your report means and why there is a BI-RADS classification system. Let me know if this makes sense in the comments below!