Surgical Pathology Criteria

Juvenile Fibroadenoma of the Breast

Differential Diagnosis

(Adult Type) Fibroadenoma Juvenile Fibroadenoma
Hypocellular to variably cellular stroma Uniformly hypercellular stroma


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


Juvenile Fibroadenoma Juvenile Papillomatosis
Cellular stroma Paucicellular stroma
Canalicular and tubular epithelium Prominent cysts


Pubertal Macromastia Juvenile Fibroadenoma
Diffuse, not circumscribed Circumscribed
Fibrous or fatty stroma Cellular stroma
Rare More common as a cause of adolescent breast enlargement
Both may cause rapid, massive growth

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