NME Distribution — Regional
Regional NME describes enhancement that occupies a volume of the breast that is typically more than one quadrant but is not diffuse and does not follow a segmental or linear distribution.
Definition
Enhancement that occupies more than one quadrant of the breast but does NOT:
- Fill 2+ quadrants (that would be diffuse)
- Follow a segmental (cone/triangular, apex toward nipple) distribution
- Follow a linear (ductal) distribution
Key Distinction
Regional distribution = large volume, no ductal/segmental pattern. This sets it apart from segmental (ductal anatomy) and linear (single duct/branch).
Imaging Appearance
- Large area of enhancement involving more than one quadrant
- Enhancement is not geometrically consistent with a breast segment or duct
- May have heterogeneous, homogeneous, or clumped internal pattern
Differential Diagnosis
| Diagnosis | Supporting Features |
|---|---|
| IDC | Regional heterogeneous NME; associated mass possible |
| DCIS | Regional heterogeneous NME |
| ILC | Regional heterogeneous; ILC diffusely infiltrates |
| Mixed invasive carcinoma | Regional homogeneous NME |
| BPE | Symmetric, bilateral; physiologic pattern |
| Adenosis/sclerosing adenosis | Regional; typically benign |
Examples from Source
- Regional, heterogeneous NME → IDC and DCIS
- Regional, homogeneous NME → Invasive carcinoma with mixed ductal and lobular features + DCIS
- Regional, heterogeneous NME → DCIS
- Regional, clumped NME → DCIS with microinvasion (+ axillary lymphadenopathy)
Board Pearl
Regional NME is suspicious-favoring. A large region of NME spanning more than one quadrant without a clear benign explanation warrants biopsy.