A 42-year-old woman has a 3 cm breast mass. Excision biopsy shows a biphasic tumor with benign glandular elements and hypercellular stroma. The stroma shows moderate cellularity, 5 mitoses per 10 HPF, and pushing (non-infiltrative) borders. Which is the most appropriate diagnosis?
- A Fibroadenoma
- B Benign phyllodes tumor ✓
- C Malignant phyllodes tumor
- D Periductal stromal sarcoma
Correct answer: B. Benign phyllodes tumor
Explanation
Phyllodes tumor is a biphasic tumor with benign glands and hypercellular stroma. Benign phyllodes shows moderate stromal cellularity, ≤5 mitoses/10 HPF, and pushing borders. Malignant phyllodes has marked cellularity, >10 mitoses/10 HPF, and infiltrative borders. Fibroadenoma has low stromal cellularity with no leaf-like architecture. Periductal stromal sarcoma is a distinct entity without phyllodes architecture.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.