A 44-year-old woman presents with a rapidly enlarging 8 cm firm breast lump of 4 months duration. The overlying skin is stretched but not tethered. Excision biopsy shows a biphasic tumour with leaf-like epithelial fronds and marked stromal cellularity with mitotic activity. What is the most likely diagnosis?

• A Fibroadenoma
• B Phyllodes tumour ✓
• C Invasive ductal carcinoma
• D Cystosarcoma with ductal ectasia

Explanation

A rapidly enlarging, large, well-circumscribed breast lump in a middle-aged woman with histology showing a biphasic lesion with leaf-like architecture and cellular stroma is a phyllodes tumour. Unlike fibroadenoma, the stroma is the driving component and shows increased cellularity and mitoses; phyllodes also recurs locally if excision margins are inadequate. Invasive ductal carcinoma would show malignant epithelial cells without leaf-like fronds, which excludes option C.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.