A 28-year-old woman presents with a firm, well-defined, mobile 3 cm lump in the upper outer quadrant of the left breast. Ultrasound shows a homogeneous hypoechoic lesion with gentle lobulation and no calcifications. FNAC shows phyllodes-like spindle stroma. The feature that most reliably distinguishes a cellular fibroadenoma from a borderline phyllodes tumour on core biopsy is:
- A Presence of intracanalicular pattern
- B Stromal hypercellularity with subepithelial condensation and leaf-like architecture ✓
- C Periductal fibrosis only
- D Epithelial hyperplasia without atypia
Correct answer: B. Stromal hypercellularity with subepithelial condensation and leaf-like architecture
Explanation
The hallmark of phyllodes tumour on histology is leaf-like (phyllodes) architecture with intracanalicular growth pattern AND stromal hypercellularity with subepithelial stromal condensation (perithelial accentuation). Fibroadenomas also have intracanalicular pattern but lack stromal hypercellularity with perithelial condensation. The leaf-like architecture itself is not sufficient — the stromal features differentiate phyllodes from cellular fibroadenoma on core biopsy.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.