Juvenile Fibroadenoma of the Breast
Circumscribed, often large, breast mass usually occuring in adolescent females with stromal and epithelial hypercellularity but lacking the leaf-like growth pattern of phyllodes tumors
Benign cystosarcoma phyllodes
Biphasic stromal and epithelial process
Pericanalicular pattern most common
May be mixed with intracanalicular
Lacks leaf-like growth pattern
Uniformly hypercellular stroma
Fibrotic areas may be present
Lacks atypical features
No periductal increase in cellularity
No stromal overgrowth
No cytologic atypia
Mitotic rate < 3/10 hpf
Frequent epithelial and myoepithelial hyperplasia
May mimic that seen in gynecomastia
May be atypical
Most patients age 10-20
(Most fibroadenomas in adolescents are typical, adult type
fibroadenomas and should be diagnosed as such) Giant fibroadenoma
Tumors >500 g or disproportionally large compared to rest of breast
More frequent in young and black patients
We consider the term merely descriptive
May be either
adult type or juvenile fibroadenomas
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting:: May 27, 2006
CD34, Factor XIIIa positive
Smooth muscle actin positive more often than in adult fibroadenoma
The histologic border between these two is not always sharp
Stromal overgrowth defined as at least one low power field (40x total magnification) composed entirely of stroma
High Grade Phyllodes Tumor
No stromal atypia
Stromal mitotic rate < 3/10 hpf
Elevated stromal mitotic rate
No stromal overgrowth
Does not infiltrate
May infiltrate surrounding breast
Both may cause rapid, massive growth
Mean age 15
More common in black females
Multiple tumors uncommon
Frequent rapid growth
May recur, especially in patients with multiple tumors
No invasion or metastases
No increased risk of carcinoma
Biphasic lesions of the breast
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