Surgical Pathology Criteria

Phyllodes Tumor of the Breast

Differential Diagnosis

Juvenile Fibroadenoma Low Grade Phyllodes Tumor
No leaf-like architecture Prominent leaf-like architecture
No condensation around ducts Stromal condensation around ducts
Does not infiltrate May infiltrate surrounding breast
The histologic border between these two is not always sharp

 

Juvenile Fibroadenoma High Grade Phyllodes Tumor
No stromal atypia Atypical stroma
Stromal mitotic rate < 3/10 hpf Elevated stromal mitotic rate
No stromal overgrowth Stromal overgrowth
Does not infiltrate May infiltrate surrounding breast
Stromal overgrowth defined as at least one low power field (40x total magnification) composed entirely of stroma

Fibroadenoma Low Grade Phyllodes Tumor
Lacks significant stromal hypercellularity Hypercellular stroma is prominent
No stromal overgrowth May have stromal overgrowth
No leaf-like architecture Prominent leaf-like architecture
No condensation around ducts Stromal condensation around ducts
Does not infiltrate May infiltrate surrounding breast
The histologic border between these two is not always sharp

Metaplastic Carcinoma Phyllodes Tumor
Spindled component may be positive for high molecular weight keratin or p63 Stromal component negative for high molecular weight keratin and p63
Epithelial component is malignant Epithelial component is benign
Squamous differentiation may be present No squamous differentiation

Pure Sarcoma of the Breast

 

Fibromatosis

 

Myofibroblastoma

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