NME Distribution — Differential Diagnosis by Distribution
This page summarizes the differential diagnosis for each NME distribution pattern.
Distribution-Based DDx Summary
| Distribution | Most Suspicious For | Common Benign Causes |
|---|---|---|
| Diffuse | IDC, ILC, inflammatory carcinoma, DCIS with microinvasion | Marked BPE |
| Regional | IDC, DCIS, ILC, mixed carcinoma | Adenosis, fibrocystic change, asymmetric BPE |
| Focal | DCIS, IDC | PASH, fibrocystic change, BPE |
| Linear | DCIS, LCIS | Stromal fibrosis, adenosis, apocrine metaplasia |
| Segmental | DCIS (extensive), invasive carcinoma | Very rarely benign |
Suspicion Ranking (Most to Least Suspicious)
- Segmental — highly suspicious; extensive ductal spread
- Linear — suspicious; single duct/branch involvement
- Regional — suspicious; large volume non-ductal
- Diffuse — suspicious but must exclude bilateral BPE
- Focal — least suspicious; but clumped focal NME still warrants evaluation
Linear vs Segmental: Key Distinction
| Feature | Linear | Segmental |
|---|---|---|
| Geometry | Line/branch | Cone/triangle |
| Apex orientation | Any | Toward nipple |
| Volume | Single duct | Duct + all branches |
| Typical pathology | Limited DCIS | Extensive DCIS |
DDx for NME + Internal Pattern Combinations
| Distribution + Pattern | Top Differential |
|---|---|
| Segmental + clumped | DCIS |
| Segmental + clustered ring | High-grade DCIS (comedo) |
| Linear + clumped | DCIS, LCIS |
| Linear + heterogeneous | DCIS or benign ductal (fibrosis, adenosis) |
| Regional + clumped | DCIS with microinvasion |
| Focal + clumped | DCIS, fibrocystic change |
| Diffuse + clustered ring | IDC + DCIS |
| Diffuse + heterogeneous | ILC, IDC |
Board Pearl
Linear and segmental distributions are inherently suspicious regardless of internal pattern, because they imply ductal anatomy involvement. Biopsy is generally warranted for a new linear or segmental NME unless a compelling prior stability or clinical explanation exists.