BSBR breast imaging classification
Citation, DOI and article data
The British Society of Breast Radiologists (BSBR) publish with the Royal College of Radiologists a standardized classification for breast imaging in the United Kingdom. The first edition in 2009 was based on findings from the RCR Breast Group (RCRBG) 1 with the current fourth edition published in November 2019 2. This 5-point scale is used to classify the suspicion of malignant lesions, for both symptomatic and screening populations.
Each breast is scored separately, and according to the most suspicious lesion:
- 1: normal
- 2: benign
- 3: intermediate / probably benign
- 4: suspicious for malignancy
- 5: highly suspicious of malignancy
The classification system is common to the major forms of breast imaging, as well as clinical examination and pathology:
Examples of normal findings (U1/M1) include normal involutional changes, and other benign findings commonly seen on screening mammograms and non-symptomatic. These include bilateral powdery microcalcifications and small (<5 mm) well-defined nodules.
The BSBR recommend inclusion of the score within both the report and the radiological summary/opinion, e.g.:
- right breast: no abnormality; U1
- left breast: irregular right upper outer mass with indistinct margin; U4
The recommendation for any atypical or suspicious features resulting in a higher lesion score is for "further investigation". In most centers this is by using US-guided core biopsy.
Patient age is taken into consideration for forms of imaging, and particularly for the requirement of fibroadenoma biopsy. The current Royal College of Radiologists guidance 2 is if a patient is under 25 years old with a typical presumed fibroadenoma (ellipsoid, wider than tall, well-defined, <4 gentle lobulations, no calcification/shadowing, thin echogenic pseudocapsule) then no further investigation is required. Even if the above features are present and the patient is >25 years old, then diagnostic core biopsy is recommended.
The 2019 update also includes a scoring system for axillary nodal lesions, which are commonly included in lesion workup.
- A1: normal
- A3: indeterminate; nodal biopsy recommended
- A4: suspicious of malignancy; nodal biopsy recommended
- A5: highly suspicious of malignancy; nodal biopsy recommended
No agreed national threshold for nodal cortical thickness, although some units practice between 2-4 mm 2.
Comparison with other systems
The BSBR 5-point score was developed after the ACR BI-RADS which is in common usage across North America and Europe. A 2011 UK study 3, early in the use of the BSBR system, found malignancy rates as follows:
- M1 - 1.8%, M2 - 1.3%, M3 - 40.8%, M4 - 94.6%, M5 - 97.8%
- U1 - 0.4%, U2 - 1.8%, U3 - 17.7%, U4 - 88.2%, U5 - 97.1%
While the benign and highly suspicious lesions compare well (0.4% versus 0%, 97.8% versus >95%), there is some discrepancy comparing RCR with BI-RADS, as BI-RADS 4 can be attributed to indeterminate U3/M3 or suspicious U4/M4 lesions. In practical terms however, all lesions U3/M3 or above should be biopsied.
The BI-RADS nomenclature is recommended for breast MRI reporting, although the BSBR score is to be included in the opinion.
- 1. Maxwell AJ, Ridley NT, Rubin G, Wallis MG, Gilbert FJ, Michell MJ. The Royal College of Radiologists Breast Group breast imaging classification. (2009) Clinical radiology. 64 (6): 624-7. doi:10.1016/j.crad.2009.01.010 - Pubmed
- 2. Royal College of Radiologists. Guidance on screening and symptomatic breast imaging, Fouth edition. (2019). Available at: https://www.rcr.ac.uk/publication/guidance-screening-and-symptomatic-breast-imaging-fourth-edition [last accessed 03 December 2019]
- 3. K Taylor, P Britton, S O'Keeffe, M G Wallis. Quantification of the UK 5-point breast imaging classification and mapping to BI-RADS to facilitate comparison with international literature. (2014) The British Journal of Radiology. 84 (1007): 1005-10. doi:10.1259/bjr/48490964 - Pubmed