BI-RADS v2025 formally incorporates non-mass lesions into the breast ultrasound lexicon. Until now the lexicon was built around discrete masses, and abnormalities without a definable margin or shape had no agreed vocabulary — so they were described inconsistently, or not reported at all. The new descriptors classify them by distribution: segmental, linear, focal or regional, with echo pattern, posterior features and associated findings recorded alongside.
The clinical stake is that these lesions carry an overall malignancy rate high enough to warrant tissue diagnosis. They are also genuinely hard to see, and the review is honest about why: no discrete margin to anchor on, and technical factors that change the appearance — the gravitational effect of patient positioning, transducer orientation during real-time scanning, and the operator dependence of handheld acquisition. Correlation with mammography, MRI, contrast-enhanced mammography and FDG PET/CT is set out for the cases where ultrasound alone leaves the question open.
What to do about it is concrete. Learn the four distribution terms and start using them in reports now, rather than describing a non-mass finding in free text; consistent terminology is what allows a subsequent reader to tell whether a lesion has changed. Scan the region again in a second patient position and a second transducer orientation before deciding a non-mass finding is artefact. And treat a genuine non-mass lesion as an indication for tissue diagnosis rather than short-interval follow-up, unless there is a clear benign explanation.
- Use the four distribution terms — segmental, linear, focal, regional — in the report, not free text.
- Rescan in a second position and orientation before dismissing a non-mass finding.
- Record echo pattern, posterior features and associated findings, as the lexicon requires.
- Default to tissue diagnosis rather than short-interval follow-up for a genuine non-mass lesion.
- Correlate with mammography or MRI where ultrasound leaves the extent uncertain.
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