BI-RADS and Mammography Categories

Last Modified: June 12, 2009


Dear OncoLink "Ask The Experts,"
The radiologist, after reading my mammogram, has classified me as a category 4. The nurse explained that there are 5 [categories], but I neglected to ask what being a category 4 means. Does it mean that it's likely that I have cancer and they just need to confirm it, or are they just testing for it?


Carolyn Vachani RN, MSN, AOCN, OncoLink's Nurse Educator, responds:

The Breast Imaging Data Reporting System (BI-RADS®) was developed by the American College of Radiology as a way to standardize mammography reporting by radiologists. The system allows the radiologist to review the mammogram films and to give them a rating, which is easily understood by the referring doctor. The rating system is used to describe imaging features of a breast mass (i.e. how things appear on the x-ray), and thus to determine how likely it is that the mass represents breast cancer. The categories are as follows:

Category 0

Need Additional Imaging Evaluation and/or Prior Mammograms for Comparison: A dditional imaging evaluation is needed. This is almost always used in a screening situation.

Category 1

Negative: There is nothing to comment on. The breasts are symmetric, and no masses, architectural distortion, or suspicious calcifications are present.

Category 2

Benign Finding(s):

Like Category 1, this is a normal assessment, but here, the interpreter chooses to describe a benign finding in the mammography report. This may include calcified fibroadenomas, multiple secretory calcifications, fat-containing lesions (oil cysts, lipomas), intramammary lymph nodes, vascular calcifications, implants or architectural distortion clearly related to prior surgery, while still concluding that there is no mammographic evidence of malignancy.

Category 3

Probably Benign Finding - Initial Short-Interval Follow-Up Suggested:

A finding placed in this category should have less than a 2% risk of malignancy. It is not expected to change over the follow-up interval, but the radiologist would prefer to establish its stability.

Category 4

Suspicious Abnormality - Biopsy Should Be Considered:

This category is reserved for findings that do not have the classic appearance of malignancy but have a wide range of probability of malignancy that is greater than those in Category 3.

Category 5

Highly Suggestive of Malignancy - Appropriate Action Should Be Taken: (Almost certainly malignant.)

These lesions have a high probability (>95%) of being cancer. This category contains lesions for which one-stage surgical treatment could be considered without preliminary biopsy. However, current oncologic management may require percutaneous tissue sampling as, for example, when sentinel node imaging is included in surgical treatment or when neoadjuvant chemotherapy is administered at the outset.

Category 6

Known Biopsy - Proven Malignancy - Appropriate Action Should Be Taken:

This category is reserved for lesions identified on the imaging study when a biopsy of cancer is already known.

It is also important to remember that about 10% of women will be called back to have repeat mammograms or ultrasound to clarify something seen on the first test. This percentage is higher in younger women (particularly those below 40 years of age) and those having their first mammogram. This is because the density of the breast tissue and the lack of a previous film to compare to, respectively, make it more difficult for the radiologist to read the current mammogram. Only approximately 3 out of every 1000 mammograms lead to a cancer diagnosis.

Of the 10% of women who return for a repeat mammogram, only 8-10% of those will need a biopsy. And about 80% of breast biopsies turn out to be benign. The bottom line is, don't put the cart before the horse. It can be very stressful waiting for tests and results, but the odds are in your favor, so hang in there!