Phyllodes tumor of the breast is best classified histologically by which combination of features?
- A Tumor size, axillary nodal status, and hormone receptor expression
- B Epithelial component grade and Ki-67 proliferation index alone
- C Nuclear pleomorphism, mitotic rate per 10 HPF, stromal overgrowth, and tumor borders ✓
- D Presence of heterologous sarcomatous elements and lymphovascular invasion
Correct answer: C. Nuclear pleomorphism, mitotic rate per 10 HPF, stromal overgrowth, and tumor borders
Explanation
WHO classification grades phyllodes tumors (benign, borderline, malignant) based on four histological features: stromal cellularity/atypia, mitotic activity (per 10 HPF), stromal overgrowth, and tumor border characteristics (pushing vs. infiltrative). Mitoses >10/10 HPF with stromal overgrowth and infiltrative borders characterize malignant phyllodes. Hormone receptor status is not a classification criterion, and while heterologous elements may appear in malignant tumors, they alone do not define the classification.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.