NME Distribution — Segmental
Segmental NME describes enhancement that is triangular or cone-shaped with the apex pointing toward the nipple.
Definition
Enhancement that is triangular or cone-shaped with the apex pointing toward the nipple, corresponding to a breast segment (duct + all its branches).
Board Pearl
Segmental distribution is typically a suspicious feature because it suggests enhancement within or around a segment of ducts or ducts and their branches — the classic pattern of DCIS.
Imaging Appearance
- Triangular or cone-shaped volume of enhancement on axial and/or sagittal images
- Apex oriented toward the nipple
- Base toward the chest wall or posterior breast
- Enhancement fills a ductal segment including primary duct and tributary branches
Pathological Basis
Segmental enhancement reflects in situ or invasive pathology growing through an entire ductal segment:
- DCIS — most important; segmental distribution is the hallmark pattern
- Invasive carcinoma extending segmentally
- Occasionally benign entities
Why Segmental is Suspicious
A ductal segment is a defined anatomical unit. Pathologic enhancement filling an entire segment implies:
- Extensive intraductal spread (DCIS)
- Or invasive carcinoma within a segment
- Benign processes rarely fill an entire segment
Differential Diagnosis
| Diagnosis | Frequency | Supporting Features |
|---|---|---|
| DCIS | Most common | Segmental; clumped or clustered ring; no mass |
| Invasive carcinoma | Common | Segmental + associated mass possible |
| Benign fibrocystic change | Rare for segmental | Usually focal or regional |
Examples from Source
- Segmental, clumped NME → DCIS (with implant incidentally)
- Segmental, clustered ring NME → DCIS
- Segmental, heterogeneous NME → DCIS
Segmental vs Linear
| Feature | Segmental | Linear |
|---|---|---|
| Shape | Cone/triangle | Line/branch |
| Apex | Toward nipple | Not necessarily |
| Volume | Large (whole segment) | Smaller (single duct) |
| Typical pathology | DCIS (extensive) | DCIS (limited) |