What BI-RADS Changes Are on the Way for Breast MRI Reporting?

Subcategory indications for asymptomatic screening and diagnostic exams, expanded acquisition parameters, a new section for lymph node reporting and new Category 4 subdivisions are some of the proposed changes that may be coming down the pike for breast magnetic resonance imaging (MRI) updates to the Breast Imaging Reporting and Data System (BI-RADS).

In a recent lecture at the Radiological Society of North America (RSNA) conference, Wendy DeMartini, MD, professor and chief of the Breast Imaging Division in the Department of Radiology at the Stanford University School of Medicine, discussed a variety of proposed, preliminary updates to BI-RADS for breast MRI reporting. Here are a few takeaways.

1. Reporting of new cross-modality structured clinical indications and optional subcategory indications. When performing asymptomatic screening, subcategory indications could include elevated breast cancer risk, dense breasts or assessment of patients who have completed breast cancer treatment, according to Dr. DeMartini. For diagnostic workup with breast MRI, subcategory indications could include clinical findings, imaging findings, Category 3 follow-up, biopsy follow-up or implant assessment.

“There are many benefits to this across modalities. … It provides much greater clarity for the reason you are doing an examination for your patients, providers, and partners. (It also) allows separate audits by these different indications which have very different performance outcomes,” noted Dr. DeMartini. “Certainly, that is important for us (in performing) breast MRI where in the United States, we have only one code for breast MRI. There is no separate screening versus diagnostic (breast) MRI code.”

2. Revised acquisition parameters include descriptions of standard full protocol contrast-enhanced breast MRI with a least two post-contrast series, and abbreviated contrast-enhanced breast MRI, which is usually performed in less than 10 minutes and includes at least one post-contrast series. Dr. DeMartini also noted there is discussion of “faster” hybrid techniques with early high temporal series, also referred to as “ultra-fast imaging”.

3. The expanded acquisition parameters also include discussion of diffusion-weighted imaging (DWI) as a complement to dynamic contrast-enhanced (DCE) MRI for further characterization of findings seen with DCE. Dr. DeMartini noted there are no current plans to introduce BI-RADS reporting of DWI at this time but noted an international consensus statement from the European Society of Breast Imaging (EUSOBI) that provides some structure for reporting DWI.¹

4. Removal of the “focus” finding type from the BI-RADS lexicon. Dr. DeMartini noted these tiny marks of enhancement generally do not have clinical significance and are typically part of the background or other benign enhancement of the breast.

“With modern breast MRI techniques, we should be able to characterize findings of less than or equal to 5 mm as a small mass that meets criteria for a mass … or focal non-mass enhancement,” maintained Dr. Demartini.

5. Introduction of T2 signal intensity as a descriptor for masses. Dr. DeMartini noted that both benign and malignant enhancing masses can be T2 hyperintense. She added that a T2 hyperintense mass that is oval and circumscribed with dark internal septations or homogeneous internal enhancement has a very low probability of malignancy at less than 2 percent. Dr. DeMartini said radiologists should characterize T2 masses as hyperintense or not hyperintense. She said hyperintense masses are uniformly bright and as bright as a normal-appearing lymph node.

6. Addition of new section for lymph node reporting. Specifically, for breast MRI, one should note whether intramammary, axillary and internal mammary lymph nodes are normal or abnormal appearing, according to Dr. DeMartini. Based on the current evidence, Dr. DeMartini said abnormal-appearing axillary lymph nodes have subjectively asymmetric morphological features in comparison to ipsilateral or contralateral nodes, particularly when nodes are ipsilateral to current or prior breast cancer. She emphasized there is currently no quantitative threshold on breast MRI for asymmetric cortical thickening. Dr. DeMartini also added that asymmetric rounding or the absence of hila is not a sole criterion for abnormal axillary lymph nodes as this can be the case for many small normal lymph nodes.

7. Clarifying the use of BI-RADS Category 3 for breast MRI. While acknowledging multiple studies that show BI-RADS Category 3 “can be employed with malignancy rates less than or equal to 2 percent,” Dr. DeMartini said there is a lack of evidence on BI-RADS Category 3 for breast MRI in comparison to the evidence for mammography and ultrasound. Suggesting that Category 3 may be overutilized for breast MRI findings, Dr. DeMartini noted a goal of reserving Category 3 for less than 5 percent of examinations and urged caution in regard to the use of Category 3 for non-baseline examinations.

“There are some data indicating that frequencies of malignancies are higher for things assessed as Category 3 if breast MRI is not the baseline examination,” explained Dr. Demartini.²

Dr. DeMartini noted there is sufficient data to use Category 3 to describe masses that are oval, circumscribed, have homogeneous internal enhancement or dark internal septations, are T2 hyperintense, and not new or increasing in size.

8. Addition of BI-RADS Category 4 subdivisions 4A-4C. The proposed preliminary changes would include: Category 4A lesions with a 2.5 percent likelihood of malignancy; Category 4B lesions with a 27.6 percent likelihood of malignancy, and Category 4C lesions with an 83.3 percent likelihood of malignancy. Dr. DeMartini added that this risk stratification falls in line with similar BI-RADS Category 4 subcategories for mammography and ultrasound imaging. She noted the subcategories offer "potential benefits for more meaningful practice audits for rad-path correlation and for the setting of patient/provider expectations."

References

1. Baltzer P, Mann RM, Iima M, et al. Diffusion-weighted imaging of the breast - a consensus and mission statement from the EUSOBI International Breast Diffusion-Weighted Imaging working group. Eur Radiol. 2020;30(3):1436-1450.

2. Edmonds CE, Lamb LR, Mercaldo SF, Sippo DA, Burk KS, Lehman CD. Frequency and cancer yield of BI-RADS Category 3 lesions detected at high-risk screening breast MRI. AJR Am J Roentgenol. 2020;214(2):240-248.