Background Parenchymal Enhancement (BPE)
Background parenchymal enhancement (BPE) is benign, physiologic enhancement of the fibroglandular tissue on contrast-enhanced breast MRI.
Definition
BPE is the normal enhancement of fibroglandular parenchyma — common, particularly in premenopausal patients. It must be distinguished from pathologic enhancing findings.
Typical Patterns
BPE commonly appears as:
- Peripheral “picture frame” or “curtain” pattern — enhancement at the periphery of the breast
- Scattered dots of enhancement throughout the breast
- More complex patterns including somewhat mass-like and non-mass-like areas
Assessment
- Assessed subjectively on early post-contrast images (60–120 seconds after contrast)
- Based on the qualitative proportion of fibroglandular tissue demonstrating benign-appearing enhancement
- Subtraction images: check for motion between pre- and post-contrast series, as motion misregistration produces artifactual “pseudoenhancement”
Level Categories (Four)
| Level | Description |
|---|---|
| Minimal | Includes no enhancement; least amount of enhancing parenchyma |
| Mild | Small amount of enhancing fibroglandular tissue |
| Moderate | Substantial enhancing parenchyma |
| Marked | Extensive enhancement throughout fibroglandular tissue |
Symmetry
BPE may be symmetric or asymmetric.
- Reporting symmetry is optional
- If asymmetric: assign BPE level to each breast individually OR use the higher level overall
Common Causes of Asymmetric BPE
- Prior ipsilateral partial mastectomy + radiation therapy → lower BPE ipsilaterally
- Asymmetric amounts of fibroglandular tissue
Board Pearl
Asymmetric BPE with lower ipsilateral BPE after lumpectomy + radiation is an expected, benign finding — do not mistake for a mass or NME.
Clinical Relevance
- Pathologic enhancing findings (masses, NME) must be morphologically unique and distinct from BPE to be considered significant
- High BPE (moderate or marked) can reduce conspicuity of enhancing lesions — a known limitation of breast MRI timing related to menstrual cycle phase