Associated Feature — Skin Retraction
Skin retraction is defined as the skin being pulled inward abnormally, creating a visible concavity or dimpling of the skin surface. The mechanism involves traction on Cooper’s ligaments or the overlying dermis by an underlying lesion or scar. In BI-RADS v2025, skin retraction is listed as associated feature #3 under the MRI lexicon (BI-RADS MRI p. 109).
Definition
- Focal inward displacement of the skin surface toward an underlying process
- Caused by shortening or fibrosis of Cooper’s ligaments or direct tethering by tumor/scar
- Distinct from skin thickening (morphologic change only, no inward pull) and skin involvement (definitive enhancement extending into the skin)
Imaging Appearance
MRI Sequences
- Fat-suppressed post-contrast T1W (early phase): Best sequence to identify skin retraction — the enhancing skin is pulled inward toward an underlying lesion. Evaluate whether the underlying lesion enhances (suspicious) or not (postsurgical)
- T2W / STIR: May show the tethered skin and underlying edema or seroma at a surgical site
- Non-contrast T1W: Can demonstrate the morphologic contour deformity; important to distinguish from skin thickening alone
- DWI: Not directly useful for skin retraction itself, but assess the underlying mass for restricted diffusion if present
Key Imaging Features
- Look for a V-shaped or tented contour of the skin pointing inward
- Evaluate the underlying cause: enhancing mass (suspicious) vs. non-enhancing scar/seroma (benign postsurgical)
- Check for associated skin enhancement — if present, this upgrades to Associated Feature — Skin Involvement
- Note whether there is an associated spiculated mass — the combination of Mass Margin — Spiculated + skin retraction is highly suspicious
Board Pearl
Skin retraction without skin enhancement is a critical distinction. In BI-RADS v2025 Figure 1 (p. 109), a round spiculated thick rim enhancing mass causes skin retraction but there is no skin enhancement — skin retraction and skin involvement are separate descriptors with different implications.
Etiologies
| Etiology | Mechanism | Distinguishing Features |
|---|---|---|
| Invasive ductal carcinoma (IDC) | Desmoplastic reaction → Cooper’s ligament shortening | Enhancing spiculated mass, often with associated peritumoral edema |
| Invasive lobular carcinoma (ILC) | Diffuse infiltration with desmoplasia | May have subtle or no mass; NME pattern; retraction may be the dominant finding |
| Prior surgery / scarring | Fibrosis and scar contracture | No abnormal enhancement; seroma at surgical site; stable on prior exams |
| Fat necrosis | Post-traumatic or postsurgical fibrosis | Peripheral enhancement with internal fat signal on non-fat-suppressed T1W; often at surgical site |
| Radiation therapy | Post-treatment fibrosis | Diffuse skin thickening + retraction in radiation field; history confirms |
Differential Diagnosis: Malignant vs. Benign Skin Retraction
| Feature | Malignant | Benign (Postsurgical) |
|---|---|---|
| Underlying enhancement | Suspicious mass or NME | No abnormal enhancement (scar/seroma) |
| Stability on priors | New or progressive | Stable |
| Skin enhancement | May be present (→ skin involvement) | Absent |
| Associated findings | Spiculation, peritumoral edema, axillary LAD | Seroma, architectural distortion at scar |
| Clinical history | No prior surgery at site | Prior surgery at site |
Board Pearl
ILC is the classic “skin retraction without obvious mass” scenario. Invasive lobular carcinoma can cause prominent skin retraction with only subtle NME or architectural distortion on MRI. If you see skin retraction without a clear mass, search carefully for ILC — it is the great mimicker.
Clinical Significance
- In the absence of suspicious findings and particularly when stable, skin retraction alone is not suspicious (BI-RADS v2025, p. 109)
- When associated with an underlying suspicious mass or NME, skin retraction supports a malignant assessment and affects T-staging
- Skin retraction alone does not constitute T4b staging — direct skin invasion (Associated Feature — Skin Involvement) is required for T4b
- Important for surgical planning: location and degree of retraction influence cosmetic outcome and reconstruction approach
Staging Implications
- Skin retraction by itself does not change T-stage — it is an associated feature, not an invasion criterion
- If the underlying tumor directly invades skin (enhancement extending into skin), this becomes skin involvement → T4b
- Always report skin retraction separately from skin involvement in structured reporting
Pitfalls
- Confusing skin retraction with skin involvement: Retraction = morphologic pulling inward; involvement = definitive skin enhancement. The two may coexist but are reported separately
- Overlooking ILC: Subtle or absent mass with prominent skin retraction — always search for a diffuse infiltrating process
- Attributing retraction to surgery without comparing priors: New skin retraction at a surgical site may indicate recurrence — always compare with prior post-treatment baseline
- Ignoring contralateral comparison: Compare skin contour with the opposite breast to confirm subtle retraction is real
- Motion artifact: Patient motion can simulate skin irregularity — confirm on multiple sequences
Board Pearl
BI-RADS v2025 explicitly illustrates benign skin retraction (Figure 4, p. 110): postsurgical scarring with seroma and no abnormal enhancement. This is the key teaching case — not all skin retraction is malignant. The absence of suspicious enhancement + stability = benign assessment.
v2025 Key Points
- Skin retraction remains listed as associated feature #3 in the v2025 MRI lexicon, consistent with the 5th edition
- The v2025 text reinforces the principle that context determines suspicion: retraction alone in the absence of suspicious findings and when stable is not suspicious
- Four figure examples in v2025 demonstrate the spectrum: IDC-associated (Figures 1-2), ILC-associated (Figure 3), and benign postsurgical (Figure 4)