Mass Margin — Spiculated
Spiculated margin indicates lines radiating from the mass — the most suspicious mass margin descriptor.
Definition
The margin is characterized by lines radiating from the mass. This is the most suspicious mass margin for malignancy.
Imaging Appearance
- Fine lines (spicules) extending outward from the mass periphery into surrounding breast tissue
- Creates a “star-burst” or “sunburst” pattern
- The lines represent desmoplastic reaction and tumor infiltration along tissue planes
- Best seen on fat-suppressed early post-contrast T1W images
Suspicion Level
Most suspicious margin descriptor. Spiculated margin has the highest positive predictive value for malignancy of all mass margin descriptors.
Association with Malignancy
- Invasive ductal carcinoma — classic spiculated, irregular mass
- Invasive lobular carcinoma — can be spiculated; often irregular spiculated
- Architectural distortion is related concept on mammography
Common Combinations in Source Figures
- Irregular + spiculated + heterogeneous → IDC
- Irregular + spiculated + thick rim enhancement → Invasive lobular carcinoma (ILC)
- Irregular + spiculated + homogeneous → IDC (homogeneous can occur)
Associated Features to Look For
When a spiculated mass is identified, evaluate for:
- Skin retraction or skin involvement
- Nipple retraction
- Pectoralis muscle involvement
- Axillary lymphadenopathy
Board Pearl
Spiculated margin is the single most suspicious individual mass descriptor on breast MRI. A spiculated mass should be considered highly suspicious for malignancy (BI-RADS 4C or 5) unless there is a compelling benign explanation (e.g., post-surgical scar).
Benign Causes of Spiculation (Rare)
- Post-surgical scar — architectural distortion/spiculation at lumpectomy site; often non-enhancing
- Fat necrosis — can create spiculation; often T1 bright fat signal helps