Mass Descriptors
Shape
| Descriptor | Implication |
|---|---|
| Oval (1–3 lobulations) | Most likely benign — suggests fibroadenoma or cyst |
| Round | Usually benign; can be cyst or fibroadenoma |
| Irregular | Concerning — raises suspicion for malignancy |
Margin
| Descriptor | Implication |
|---|---|
| Circumscribed | Well-defined, abrupt interface — favors benign (cyst, fibroadenoma) |
| Obscured (≥25% hidden) | Overlapping tissue — needs further evaluation |
| Microlobulated | Short-cycle undulation — suspicious, BI-RADS ≥4A |
| Indistinct | No clear demarcation — suspicious |
| Spiculated | Most suspicious — radiating lines, highly associated with malignancy or radial scar |
Density
| Descriptor | Implication |
|---|---|
| High density | Denser than equivalent breast tissue — suspicious feature |
| Equal density | Isoechoic to glandular tissue |
| Low density | Less dense than equivalent tissue |
| Fat-containing | Benign: lipoma, hamartoma (mixed density), oil cyst, lymph node (fatty hilum) |
Spiculated margin is the single most suspicious mammographic feature — regardless of size or density. Fat-containing masses are virtually always benign and require no biopsy.
Architectural Distortion and Asymmetries
| Finding | Definition | Malignancy Risk | Action |
|---|---|---|---|
| Architectural Distortion | Tethering/retraction of parenchyma without a visible mass; spiculation at a focal point | ~20–30% (if not post-surgical) | Diagnostic workup + ultrasound; biopsy if no prior surgery at site. Radial scar on DBT → surgical excision. |
| Asymmetry | Seen in ONE projection only; not a mass; no central density or architectural distortion | Very low | Typically benign tissue overlap; spot compression views to confirm |
| Global Asymmetry | Asymmetric density involving >¼ of the breast; no architectural distortion or suspicious features | Very low | Usually normal variant; correlate with clinical exam; prior comparisons essential |
| Focal Asymmetry | Seen in BOTH projections; no central density/mass; no calcifications or distortion; smaller than global | ~1–2% | Diagnostic workup; spot compression ± US; BI-RADS 0 on screening → diagnostic mammo + US |
| Developing Asymmetry | NEW or LARGER focal asymmetry compared to prior exam | ~15% | Biopsy recommended — highest risk of all asymmetries; BI-RADS 4A at minimum after diagnostic workup confirms persistence |
Developing asymmetry: Even if the diagnostic workup (US, spot compression) is unremarkable, a developing asymmetry that persists warrants tissue sampling. ~15% malignancy rate exceeds the BI-RADS 3 threshold. Stereotactic or tomosynthesis-guided biopsy may be required if US is negative.
Digital Breast Tomosynthesis (DBT) Pearls
- DBT reduces recall rate by ~15–40% compared to 2D mammography alone by resolving summation artifact
- DBT increases cancer detection rate by ~25–40%, particularly for invasive cancers
- DBT does not replace magnification views for calcification workup
- Architectural distortion is better detected on DBT than 2D — its detection should increase recall for biopsy