The Mammogram Report: The Breast Imaging Reporting and Data System (BI-RADS™) Lexicon
Appropriateness of Short-Term Follow-Up Mammography for “Probably Benign” Lesions
The use of short-term follow-up mammography for BI-RADS™ Category 3 (“probably benign”) lesions has been well supported in the literature.
Examples of such lesions include single or multiple circumscribed masses and single or multiple groups of rounded or punctate calcifications.
Table 6.3. Breast imaging reporting and data system (BI-RADS™) final assessment categories
a. Assessment is incomplete
Category 0
Need additional imaging evaluation:
Finding for which additional imaging evaluation is needed. This is almost always used in a screening situation and should rarely be used after a full imaging workup A recommendation for additional imaging evaluation includes the use of spot compression, magnification, special mammographic views, ultrasound, etc.
The radiologist should use judgement in to how vigorously to pursue previous studies.
b.Assessment is complete - final categories
Category 1
Negative:
There is nothing to comment on. The breasts are symmetrical and no masses, architectural disturbances or suspicious calcifications are present.
Category 2
Benign Finding:
This is also a negative mammogram, but the interpreter may wish to describe a finding. Involuting, calcified fibroadenomas, multiple secretory calcifications, fatcontaining lesions such as oil cysts, lipomas, galactoceles, and mixed-density hamartomas all have characteristic appearances and may be labeled with confidence. The interpreter might wish to describe intramammary lymph nodes, implants, etc., while still concluding that there is no mammographic evidence of malignancy.
Category 3
Probably Benign Finding - Short Interval Follow-up Suggested:
A finding placed in this category should have a very high probability of being benign. It is not expected to change over the follow-up interval, but the radiologis would prefer to establish its stability. Data are becoming available that shed light on the efficacy of short interval follow-up. At the present time, most approaches ar intuitive. These will likely undergo future modification as more data accrue as to the validity of an approach, the interval required and the type of findings that should be followed.
Category 4
Suspicious Abnormality - Biopsy Should Be Considered:
These are lesions that do not have the characteristic morphologies of breast cance but have a definite probability of being malignant. The radiologist has sufficient concern to urge a biopsy. If possible, the relevant probabilities should be cited so that the patient and her physician can make the decision on the ultimate course of action.
Category 5
Highly Suggestive of Malignancy - Appropriate Action Should Be Taken:
These lesions have a high probability of being cancer.
In previous studies, the frequency of carcinoma for BI-RADS™ Category 3 lesions has ranged from 0.5-2.0%.
Sickles recommended short-term follow-up mammography in 3,184 “probably benign” lesions; cancer was subsequently discovered in 17 (0.5%).
Fifteen of the 17 cancers were diagnosed by means of interval change at follow-up mammography before they were palpable; all 17 were Stage 0 or Stage I at the time of diagnosis (one positive axillary lymph node was present in two patients). These data support the utility of the short-term follow-up mammogram in the management of “probably benign” lesions. The likelihood of cancer in this setting is extremely low, and if present it is likely that it will be diagnosed at an early and treatable stage.
More recently, Sickles has extended his work to address the question of whether patient age or lesion size should prompt immediate biopsy of nonpalpable, circumscribed, solid nodules. Of 1,403 circumscribed masses included in this study, cancer was found in 19 (positive predictive value [PPV]=1.4%). Only small differences in PPV were found for various patient age and lesion size subgroups. Even in the group of women age 50 and older, the ratio of benign to malignant was 60:1 (PPV=1.7%). These data suggest that lesion size and patient age should not deter the clinician from recommending short-interval follow-up mammography for “probably benign” lesions.
Positive Predictive Value of BI-RADS™ Categories
The BI-RADS™ categories are useful predictors of malignancy. The frequency of carcinoma is 29-34% for BI-RADS™ Category 4 (suspicious abnormality) and 81-94% for BI-RADS™ Category 5 (highly suggestive of malignancy). Biopsy is generally recommended for BI-RADS™ Category 4 and Category 5 lesions. For nonpalpable masses, biopsy can be performed with needle localization and surgical biopsy or image-guided percutaneous breast biopsy.
Laura Liberman and Timothy L. Feng
Breast cancer detection demonstration project: five-year summary report. CA 2003