## Distinguishing Fibroadenoma from Phyllodes Tumour ### Key Clinical and Pathological Differences **Key Point:** Rapid growth and large size (>5 cm) is the most reliable clinical discriminator between fibroadenoma and phyllodes tumour, as fibroadenomas grow slowly and remain <3 cm in most cases, whereas phyllodes tumours characteristically enlarge rapidly. ### Comparison Table | Feature | Fibroadenoma | Phyllodes Tumour | | --- | --- | --- | | **Growth rate** | Slow, stable | Rapid, progressive | | **Size at presentation** | Usually <3 cm | Often >5 cm | | **Age of onset** | 15–35 years | 40–50 years | | **Histology** | Epithelial + stromal proliferation | Leaf-like stromal architecture | | **Malignant potential** | None | Yes (10–15% borderline/malignant) | | **Clinical behaviour** | Benign, static | Benign to malignant spectrum | | **Palpability** | Mobile, well-defined | Mobile, well-defined | ### Why Rapid Growth is the Best Discriminator 1. **Clinical presentation:** A young woman with a slowly enlarging breast mass over months is likely fibroadenoma; a mass that doubles in size over weeks to months suggests phyllodes. 2. **Prognostic implication:** Rapid growth mandates urgent imaging and biopsy to exclude malignancy. 3. **Management trigger:** Size >5 cm + rapid growth = excision mandatory; stable fibroadenoma <3 cm = observation acceptable. **Clinical Pearl:** A fibroadenoma may remain unchanged for years; a phyllodes tumour that grows rapidly is a red flag for stromal overgrowth and potential malignant transformation. **High-Yield:** Remember the "5 cm rule"—any breast mass >5 cm with rapid growth is phyllodes until proven otherwise. 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.