Radial scar

General features

• Definition: Benign breast lesion characterized by a fibroelastic core with radiating ducts and lobules.
  • Radial scar: < 10 mm.
  • Complex sclerosing lesion (CSL): > 10 mm.
• Epidemiology: Common, often incidental finding in screening population (40–60 years).
• Pathology:
  • Pseudo-infiltrative appearance mimicking carcinoma.
  • Central fibroelastotic core containing entrapped glandular structures.
  • Peripheral radiating ducts often show epithelial hyperplasia, adenosis, or ectasia.
• Malignancy risk:
  • Classified as a B3 lesion (lesion of uncertain malignant potential).
  • Associated with malignancy (DCIS or invasive carcinoma) in 10–30% of cases (upgrade rate).
  • Independent risk factor for future breast cancer (approx. 2x risk).

Imaging features

Mammography

• Appearance: Spiculated mass or architectural distortion.
• "Black star" sign: Radiating long, thin spicules with a central radiolucency.
  • Contrast with carcinoma ("White star"): Carcinomas typically exhibit a central density.
• Planar configuration: Appearance varies significantly between CC and MLO views (looks like a thin line on one view and a mass on the other), suggesting a flat, disc-like shape.
• Calcifications: Can be present (usually benign-appearing, but pleomorphic if associated DCIS).
• Absence of secondary signs: rarely causes skin thickening or nipple retraction compared to similar-sized carcinomas.

Ultrasound

• Appearance: Variable and often non-specific.
• Can be sonographically occult.
• Ill-defined hypoechoic area or architectural distortion.
• Posterior acoustic shadowing is common.
• Note: Differentiating from invasive carcinoma on US alone is rarely possible.

MRI

• Morphology: Spiculated enhancing mass or non-mass enhancement.
• Kinetics: Variable. Can show rapid uptake and washout (type 3 curve), mimicking malignancy, or progressive enhancement.
• Utility: Limited for differentiating from carcinoma; primarily used if staging is required for concurrent disease.

Differential diagnosis

1. Invasive breast carcinoma: Specifically tubular carcinoma (often indistinguishable imaging features) or invasive ductal carcinoma (NOS).
2. Post-surgical scar: History of surgery is key; usually decreases in size/density over time.
3. Fat necrosis: Usually radiolucent center (oil cyst) with history of trauma.
4. Sclerosing adenosis.

Management

1. Diagnosis: requires histological confirmation.
2. Intervention:
   • Vacuum-assisted biopsy (VAB): Gold standard for diagnosis and sampling. RCR/NHS BSP guidelines suggest VAB to excise the lesion (therapeutic biopsy) or extensively sample it.
   • Surgical excision:
     • Historically the standard of care.
     • Currently indicated if:
       • Atypia is found on biopsy (e.g., ADH, LIN).
       • Radiologic-pathologic discordance.
       • Lesion is too large for complete VAB removal.
   • Surveillance: Emerging evidence suggests small (<1-2 cm), asymptomatic radial scars without atypia on extensive VAB sampling may be safely observed, but this decision must be made by a specialist MDT.
3. Consensus:
   • If question asks for "Next step" after CNB shows radial scar: VAB excision or Surgical excision.
   • Do not select "discharge" or "routine screening" immediately after CNB.

Exam pearls

• Aunt Minnie: "Black star" on mammogram (spiculated mass with dark center).
• The Trap: Do not assume it is benign based on the "central lucency" appearance alone. Biopsy is mandatory.
• Association: Most commonly associated with tubular carcinoma (a low-grade invasive cancer).
• Distinction: Radial scar vs. CSL is purely a size cutoff (10 mm).