Juvenile Fibroadenoma of the Breast

Definition

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

Circumscribed
- Rarely multiple
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