NME Distribution — Linear
Linear NME describes enhancement arrayed in a line — which may be straight, curved, angled, or branching.
Definition
Enhancement arrayed in a line (which may curve or be angled) or a line that branches.
Board Pearl
Linear distribution is typically a suspicious feature because it suggests enhancement within or around a duct.
Imaging Appearance
- Enhancement follows a line or branching pattern on axial and/or sagittal images
- The line extends toward or away from the nipple, following a ductal course
- May branch (like a tree or branching duct)
- Does not have the cone/triangular volume of segmental NME
Pathological Basis
Linear enhancement reflects tumor or pathologic tissue growing within or around a single duct or ductal branch, most often:
- DCIS — in situ carcinoma growing within ducts
- Invasive carcinoma extending along ducts
- Occasionally benign ductal processes (adenosis, fibrosis, apocrine metaplasia)
Differential Diagnosis
| Diagnosis | Supporting Features |
|---|---|
| DCIS | Most common; linear or linear-branching; clumped pattern |
| LCIS | Linear NME; can be challenging to distinguish from DCIS |
| Stromal fibrosis | Linear heterogeneous NME; benign |
| Sclerosing adenosis | Linear heterogeneous NME; benign |
| Apocrine metaplasia | Linear heterogeneous NME; benign |
Examples from Source
- Linear, homogeneous NME → DCIS
- Linear, clumped NME → DCIS
- Linear, clumped NME → LCIS
- Linear, heterogeneous NME → Stromal fibrosis (benign)
- Linear, heterogeneous NME → Nodular sclerosing adenosis (benign)
- Linear, heterogeneous NME → Apocrine metaplasia (benign)
Linear vs Segmental
| Feature | Linear | Segmental |
|---|---|---|
| Shape | Line/branch | Cone/triangle |
| Apex toward nipple | Not necessarily | Yes |
| Volume | Small | Larger |
| Pattern | Single duct | Duct + branches |