Associated Feature — Nipple Retraction
The nipple is pulled inward by an underlying pathologic process. This must not be confused with nipple inversion, which is typically bilateral and a normal developmental variant.
Definition
Nipple retraction is the unilateral inward displacement of the nipple caused by traction from an underlying lesion — most commonly a mass or area of fibrosis pulling on the ductal structures and Cooper ligaments. In BI-RADS v2025, nipple retraction is classified as an associated feature — a secondary sign that modifies the suspicion of a primary finding but is not itself a finding category.
Imaging Appearance
T1-Weighted (Pre-Contrast)
- Loss of the normal nipple contour with inward angulation
- The nipple-areolar complex may appear flattened or pulled below the skin surface
- Compare with the contralateral side for asymmetry
T2-Weighted
- The retracted nipple may show low T2 signal when caused by desmoplastic fibrosis
- Surrounding periareolar edema (high T2 signal) may be present in malignant cases
- Benign post-surgical retraction typically lacks periareolar edema
Post-Contrast (DCE-MRI)
- Evaluate for an enhancing mass or NME along the ductal axis extending toward the nipple
- Enhancing tissue tracking from a deeper lesion to the nipple supports malignant retraction
- Skin enhancement and thickening adjacent to the retracted nipple raises concern for inflammatory or locally advanced carcinoma
DWI
- Restricted diffusion in tissue deep to the retracted nipple suggests underlying malignancy
- DWI adds specificity when post-contrast findings are equivocal
Etiologies
- Malignant: underlying carcinoma (IDC, ILC) pulling the nipple via direct invasion or desmoplastic reaction; ILC is particularly notorious due to its diffuse, infiltrative growth pattern
- Post-surgical: scarring and fibrosis from prior biopsy, lumpectomy, or reduction mammoplasty
- Inflammatory: periductal mastitis, duct ectasia with periductal fibrosis
- Congenital: developmental nipple inversion (bilateral, stable, non-pathologic)
| Etiology | Laterality | Stability | Associated Findings |
|---|---|---|---|
| Carcinoma (IDC/ILC) | Unilateral | New or progressive | Enhancing mass, NME, skin thickening |
| Post-surgical scarring | Unilateral | Stable | Fat necrosis, architectural distortion at surgical site |
| Periductal mastitis | Unilateral | May fluctuate | Subareolar abscess, ductal dilation, skin thickening |
| Congenital inversion | Bilateral | Lifelong | None — normal variant |
Clinical Significance
- In the absence of suspicious findings and particularly when stable on comparison imaging, nipple retraction alone is not suspicious and should not upgrade assessment
- When associated with an underlying mass, NME, or architectural distortion, nipple retraction supports a suspicious assessment (BI-RADS 4 or 5)
- New-onset unilateral nipple retraction warrants careful evaluation of the retroareolar and central breast regions
- Important for surgical planning — nipple retraction may indicate central breast involvement requiring central lumpectomy or mastectomy rather than nipple-sparing approaches
- In the setting of neoadjuvant chemotherapy, persistent nipple retraction after treatment does not necessarily indicate residual disease — fibrosis may cause permanent retraction
Board Pearl
Nipple retraction ≠ nipple inversion. Retraction = unilateral, pulled in by a pathologic process. Inversion = often bilateral, a normal developmental variant. On boards, always distinguish between the two — the figure legends in BI-RADS v2025 explicitly differentiate them with separate illustrations.
Board Pearl
ILC is the classic culprit. Invasive lobular carcinoma grows in single-file lines along ductal structures and Cooper ligaments, causing nipple retraction without a discrete palpable mass. When you see nipple retraction with subtle or no mass on MRI, think ILC and look for non-mass enhancement with linear or segmental distribution.
Board Pearl
Always compare with prior imaging. A new nipple retraction on MRI that was not present on prior mammogram or MRI is a red flag — even if no enhancing lesion is identified. Recommend clinical correlation and consider targeted ultrasound of the retroareolar region.
Pitfalls
- Mistaking congenital inversion for pathologic retraction — check contralateral nipple and prior imaging; bilateral symmetric inversion is almost always benign
- Overlooking ILC — ILC may cause nipple retraction with minimal or no enhancement on MRI; correlate with mammography for asymmetry or architectural distortion
- Post-surgical change mimicking malignant retraction — always check surgical history; a scar at the 12 o’clock position near the nipple can cause retraction identical in appearance to malignant retraction
- Motion artifact at the nipple — the nipple is at the breast surface where respiratory motion is maximal; confirm retraction on multiple sequences and planes
- Assuming retraction alone warrants biopsy — an isolated, stable, longstanding retraction without a suspicious underlying finding should not be upgraded; clinical context is essential
Differential Diagnosis
| Finding | Key Distinguishing Feature |
|---|---|
| Nipple inversion (normal variant) | Bilateral, symmetric, stable, no underlying lesion |
| Malignant retraction (IDC/ILC) | Unilateral, new, associated enhancing mass or NME |
| Post-surgical retraction | History of surgery, stable, scar/fat necrosis at surgical bed |
| Periductal mastitis | Subareolar inflammation, may fluctuate, skin thickening |
| Paget disease of the nipple | Nipple skin enhancement and thickening, may have underlying DCIS |
v2025 Updates
Nipple retraction remains classified as an associated feature in BI-RADS v2025, consistent with the 5th edition. The v2025 text provides explicit figure-based illustration distinguishing retraction from inversion, reinforcing this as a commonly tested distinction. The emphasis on clinical context (new vs. stable, isolated vs. associated) for determining significance is preserved.