Non-Mass Enhancement (NME)
Non-mass enhancement (NME) is a unique area of enhancement that is distinct from normal background enhancement and is not a mass.
Definition
NME may extend over small or large areas and often has interspersed areas of FGT or fat between the enhancing components. This intervening tissue distinguishes NME from masses, which are solid 3-dimensional structures.
Key Distinguishing Feature from Mass
When deciding whether to characterize enhancement as a mass or NME:
- Intervening tissue and/or fat between enhancing components → NME
- NME-type distribution pattern (e.g., segmental, linear) → NME
- Solid 3D structure with convex-outward contour → Mass
Characterization
NME is characterized morphologically by:
- Distribution (primary descriptor)
- Internal enhancement pattern (secondary descriptor)
These are assessed on the early post-contrast series. Kinetics may also help when morphology is not definitively benign or suspicious.
Minimum Description
A description should include at least distribution + internal enhancement pattern.
Distribution Categories
| Distribution | Suspicion |
|---|---|
| NME Distribution — Diffuse | Variable — can be malignant |
| NME Distribution — Regional | Suspicious-favoring |
| NME Distribution — Focal | Least suspicious; can be BPE variant |
| NME Distribution — Linear | Suspicious — ductal |
| NME Distribution — Segmental | Suspicious — ductal/segmental |
Internal Enhancement Pattern Categories
| Pattern | Notes |
|---|---|
| NME Enhancement — Homogeneous | Less suspicious |
| NME Enhancement — Heterogeneous | Nonspecific |
| NME Enhancement — Clumped | Suspicious-favoring |
| NME Enhancement — Clustered Ring | Suspicious |
Board Pearl
Linear and segmental distributions are typically suspicious because they suggest enhancement within or around ducts. These distributions raise concern for DCIS.
Pathologies Presenting as NME
| Pathology | Common NME Features |
|---|---|
| DCIS | Linear/segmental; clumped or clustered ring |
| IDC | Diffuse or regional; heterogeneous |
| ILC | Regional or diffuse; heterogeneous |
| DCIS with microinvasion | Diffuse or regional |
| Benign fibrocystic change | Focal; clumped |
| PASH | Focal; heterogeneous |
| Adenosis | Regional; variable |
| Stromal fibrosis | Linear; heterogeneous |
v2025 Change
Focus has been removed from the BI-RADS lexicon. Small enhancing foci that do not meet criteria for a mass should be characterized as focal NME if they meet NME criteria, or dismissed as benign BPE variants.
Related
- NME Distribution — Diffuse
- NME Distribution — Regional
- NME Distribution — Focal
- NME Distribution — Linear
- NME Distribution — Segmental
- NME Enhancement — Homogeneous
- NME Enhancement — Heterogeneous
- NME Enhancement — Clumped
- NME Enhancement — Clustered Ring
- Masses
- Background Parenchymal Enhancement
- Breast MRI Lexicon Overview