BI-RADS stands for Breast Imaging Reporting and Data System and was established by the American College of Radiology.
BIRADS is a scheme for putting the findings from mammogram screening (for breast cancer diagnosis) into a small number of well-defined categories. Although BIRADS started out for use with breast screening mammography, it was later adapted for use with Magnetic Resonance Imaging (MRI) and breast ultrasound (US) as well.
BIRADS is something that mainly benefits the radiologists who report mammogram (and breast MRI and US) findings. It doesn’t do anything directly useful for patients or for the doctors who referred a patient for breast imaging.
There is some updated information on BI-RADS and all aspects of breast screening on our brand new website HERE. This post concentrates only on BI-RADS.
How does BI-RADS benefit radiologists?
The benefit of BI-RADS to radiologists is that it forces them to think about which category their findings will fit into and when they assign each case a category it then becomes possible to calculate accuracy statistics.
The accuracy statistics are generally calculated once a year and they are important in quality assurance, that is they tell the radiologist whether they are doing a good job or not. This will re-assure the good radiologists to keep doing whatever they are doing, but for radiologists whose accuracy statistics are not very good, it lets them know that they ought to get more training.
BI RADS classification is not a formal requirement for radiologists to use, but most do.
Another benefit of BIRADS to radiologists, that has indirectly benefited everyone else, is that the categorization scheme has helped to standardize the words used in mammographic reporting, and this has reduced the confusion and improved communication between radiologists, patients and physicians.
BI-RADS classifications have also helped in monitoring breast cancer treatment and supporting breast cancer research again by making statistics easier to calculate.
A woman is usually not told of the BI-RADS assessment directly. However, if you do come across these terms in your report it may be useful to know what they mean.
BI RADS Mammographic Assessment Categories
The BI-RADS assessment categories are:
- 0- incomplete
- 2-benign findings
- 3-probably benign
- 4-suspicious abnormality
- 5-highly suspicious of malignancy
- 6-known biopsy with proven malignancy
After the initial breast cancer screening, a follow-up or diagnostic mammography is often recommended if the BI-RADS category is 3 or higher. By a huge majority, most breast cancer screening mammograms are classified as either BI-RADS 1 or BI-RADS 2 and those categories are nothing to worry about and require no further treatment. A lot of women over 40 will have BI-RADS categories 1 and 2 following their annual mammogram.
The postive predictive value (for confirmed breast cancer) increases at BIRADS Catetgory 4
Up to 9% of breast cancer screening mammograms will be given a BI-RADS category of 3, 4 or 5, which implies that there is cause for concern and further investigations will be needed.
BIRADS 3 is rarely used nowadays, because BIRADS 4 and 5 are categories that lead to biopsies, and breast biopsy to give a definitive diagnosis. BIRADS 3 often indicates the need for a 6-month follow-up mammogram. This can cause worry and anxiety for everyone for those 6 months due to the uncertainty of the situation. Both radiologists and patients prefer fast answers rather than having to wait for 6 months.
If a mammogram is classified into the BI-RADS category 3 it tends to have a very low positive predictive value (less than 2%), meaning the chance of being diagnosed with breast cancer is low.
A BI-RADS category 4 mammogram has a positive predictive value of about 30%. A category 5 mammogram is almost certainly predictive of breast cancer with a positive predictive value of about 95%.
BI-RADS assessment categories:
Category 0 Assessment is incomplete
Category 0 means the Assessment is not complete and additional work-up is often recommended. This can be spot compression, magnification, or breast ultrasound. Category 0 means that there is not enough information yet to complete the process. In real-life terms, if a screening mammogram shows something like a round nodule and the radiologist thinks it might be a cyst (not cancer), the radiologist will ask for an ultrasound and assign a BIRADS 0 category to the mammogram. When the ultrasound result is available, and suppose it showed a benign cyst, then the ultrasound result “completes the BIRADS” and assigns a category 2 to the case because a cyst is benign.
Category 1. Negative.
With category 1 the breast cancer screening mammogram shows no grouped or suspicious microcalcifications, no well-formed mass, asymmetrical glandular structure and/or no change from any previous exam.
Category 2, benign
Category 2 is a definitive benign finding and a routine screening. That is, there is something abnormal on mammogram but it is not breast cancer or malignant in any way.
BI-RADS category 2 findings often include:
- Round opacities with macrocalcifications (typical calcified fibroadenoma or cyst)
- Round opacities corresponding to a typical cyst at ultrasonography
- Oval opacities with a radiolucent center
- Fatty densities or partially fatty images (lipoma, galactocele, oil cyst, hamartoma )
- Surgical scar
- Scattered macrocalcifications (fibroadenoma, cyst, cytosteatonecrosis, secretory ductal ectasia);
- Vascular calcifications
- Breast implants, silicone granuloma.
|The specs are benign microcalcifications|
|Here the calcium buildup is in layers, like sediment or leaves in a teacup.|
|Round, benign microcalcification.|
Category 3. Probably Benign
With BI-RADS category 3, a follow-up of 6 months is usually recommended. On the breast cancer screening mammogram there may be a finding of some kind, but the lesion is non-palpable.
Findings typical of this category include:
- Clusters of tiny calcifications – round or oval
- Non-calcified solid nodules (no size limitation but non palpable on physical examination), round, ovoid and well-defined.
- Selected focal asymmetrical areas of fibroglandular densities (not palpable): This might include concave-outward defined margins, interspersed with fat and without central increased fibular density on two projections.
- Miscellaneous focal findings, such as a dilated duct or post biopsy architectural distortion without central density
- Generalized distribution in both breasts. For example, multiple similar lesions with tiny calcifications or nodules distributed randomly
In some scenarios a percutaneous biopsy (usually core-needle biopsy) might be considered even for BIRADS category 3. For example, extreme patient anxiety or plans for pregnancy, plans for breast augmentation or reduction surgery, or if synchronous carcinoma is present.
|These tiny specs are diffuse punctate microcalcifications.|
|This microcalcification is round but the edges are not sharply defined. It would be called ‘indeterminate BI-RADS 3 and not BI-RADS 2, because of the poorly defined, fuzzy edge.|
The positive predictive value (PPV) (the chance of having a real breast cancer) is very low for BI-RADS category 3 lesions and has actually decreased in recent years. With advances in research and experience the PPV of a category, breast lesions 3 are now considered less than 1%.
Category 4 Suspicious or Indeterminate abnormality
A BI-RADS category 4 mammogram is where concern for breast cancer risk begins to increase. A biopsy should be recommended with BI-RADS category 4. Typically, a lesion has been found but does not initially appear to have the morphological characteristics of breast cancer. BI-RADS category 4 is therefore often subdivided into there smaller sub-categories:
- BI RADS 4AThere is a low suspicion of malignancy.
- BI RADS 4B There is a moderate suspicion of malignancy.
- BIRADS 4C There is a high suspicion of malignancy.
Findings typical of BI-RADS category 4 include:
- Asymmetric, localized or evolving hyperdensities with convex contours.
- Indeterminate microcalcifications appearing amorphous and indistinct particularly if in a cluster or heterogeneous and pleomorphic
- Round or oval non cystic opacities with microlobulated or obscured contours
The positive predictive value (the chance of a real cancer) of BI-RADS 4 mammograms is thought to be around 20-40%.
|‘powderish microcalcifications are suggestive of BI-RADS classification of 4.|
|These ‘powderish’ microcalcifications appear in large clusters.|
BI-RADS category 4C has quite a high positive predictive value for breast cancer
BI-RADS category 4 is now broken in to sub-categories A, B, and C. In terms of the positive predictive value for breast cancer, a category bi-rads 4A mammogram is quite low at 13%, and category bi-rads 4B also moderately low at about 36%. But when we see a mammogram classified as bi-rads4C, the positive predictive value of breast cancer jumps up to around 79%, that means category 4C indicates a high risk for breast cancer.
The most common finding in BI-RADS category 4 is fibrocystic changes
The exact clinical significance of the sub-categorizations of BI-RADS category 4 remains a little vague. Generally speaking, as we move further into categories A,B, and finally C, the chances of the breast lesion being diagnosed as Ductal Carcinoma in Situ (DCIS) increases.
Around 70% of BI-RADS category 4C breast lesions turn out to be ductal carcinoma in situ. DCIS is found in category 4B lesions about 21% of the time and only 10% of the time with category 4A breast lesions.
In terms of the frequency of the subcategories of BI-RADS 4, it may be suggested that category 4A is seen about 50% of the time, 4B about 38% of the time and category 4C only about 13% of the time. The most common confirmed diagnostic finding in BI-RADS category 4 generally, is actually fibrocystic changes (fibrocystic disease) in around 28% of cases. DCIS is confirmed about 23% of the time with columnar cell change and fibroadenoma found in about 19% of cases.
Category 5. Highly suggestive of malignancy
A 5 BI-RADS category is assigned when there is a very high probability of breast cancer and a biopsy should be taken immediately.
Findings typical of category five include:
- Typically malignant microcalcifications; for example, linear with branching pattern; particularly if numerous, clustered and with a segmental distribution;
- Clusters of microcalcifications with a segmental or galactophorous distribution
- Evolving microcalcifications or associated with an architectural distortion or opacity
- Clusters of microcalcifications with a segmental or galactophorous distribution
- Poorly circumscribed opacities with ill-defined and irregular contours;
- Spiculated opacities with radio-opaque center.
BI-RADS category 5 is usually reserved for lesions having a 95% probability of malignancy. After biopsy the average rate of carcinoma in category 5 biopsies is about 75-97%.
|Casting microcalcifications appear linear, fragmented, and branching.|
|In this image the casting microcalcifications are branched, and granular.|
Category 6. Known Cancer
Category 6 indicates a known cancer, proven by biopsy. This category is used when patients undergoing breast cancer treatment have follow-up mammograms. For a few years after breast cancer treatment, category 6 may still be used. Since everyone already knows there is, or was, a cancer, we can’t use categories 0 thru 5 anymore, so category 6 is assigned. Category 6 isn’t useful for accuracy statistics.
Certain microcalcifications might even be ‘directly’ associated with breast cancer.
BI-RADS mammogram classifications are generalizations and tend to revolve around the presence and type of microcalcifications. Within the range of observations about the various types and patterns of breast tissue microcalcifications present, it may be suggested that coarse heterogeneous microcalcifications are positively associated with breast cancer about 7% of the time and amorphous microcalcifications about 13% of the time. Fine pleomorphic breast microcalcifications have a positive predictive value for breast cancer of about 30%, while fine linear microcalcifications are associated with confirmed breast cancer in over 50% of cases.
BI-RADS mammogram classifications are not intended as a diagnostic tool, but only as a means of standardizing communications and helping to identify situations where follow-up is required, and the most appropriate type of follow-up. The fastest and most economical way to arrive at a positive or confirmed diagnosis of breast cancer is by core needle biopsy.
- A bi-rads category 2 means the radiologist saw something that is not cancer. Something benign like a cyst.
- When to use bi rads? Only at the moment when a radiologist is finishing a report and needs to assign the findings into a category.
- How accurate are birads? Iffy, by which I mean, the words in the report are important, but the birads is an afterthought, and sometimes a clerk or assistant or a technologist just reads the radiologist report and assigns a bi-rads number onto the statistical recording data-entry field.
- How to pronounce bi rads? Bi sounds like buy, rads sounds like fads.
- What are bi rads? They are a thing to not care about, unless you are a radiologist. Or maybe you meant to type in birds, our feathered friends.
- What is the birads lexicon? Good question. This is a major contribution to progress, by limiting the allowable words that describe abnormalities on a report, it standardized things.
- Is there an atlas or a book? Yes. ACR-BIRADS Atlas is the name of the official book on the subject, now in fifth edition.
- Does high breast density affect birads? Nope. Actually, radiologists were using 4 categories of mammogram density coding before bi rads existed. Only years later, someone said, lets include these 4 breast density definitions into birads. Another factor in breast density is whether the breasts are heterogeneously dense (that is both the same).
- If further investigations are necessary, what will happen? For a definitive diagnosis a biopsy will be necessary. There are 2 main types of biopsy; surgical biopsy (or open biopsy) and needle biopsy. Most biopsies today are done with a needle under local anesthetic and are painless.
- Does BIRADS include whether the lymph nodes are involved in the breast disease? Lymph node involvement is usually more related to breast cancer staging whereby a cancer has been confirmed. BIRADS is more a screening categorization system to detect breast cancer.