Fibroadenoma

Epidemiology:

• Any reproductive age
• More common < 30
• Cyclosporine A (post-renal transplantation)
• some are polyclonal hyperplasias, others are monoclonal neoplasms of stromal cells
• epithelial component is polyclonal
• Juvenile fibroadenoma:
• adolescents

Common sites:

Gross features:

• frequently multiple and bilateral
• sharply circumscribed
• rubbery
• grayish white
• slitlike spaces often
• large lobulated “popcorn” calcifications sometimes
• juvenile fibroadenoma
• often > 5cm “giant fibroadenoma”
• may cause breast distortion

Histologic features:

• spherical nodule
• delicate, often myxoid stroma
• resembles intralobular stroma
• may be cellular
• densely hyalinized often in older women
• stroma is enclosing glandular and cystic spaces lined by epithelium
• may compress or distort the epithelium
• “complex fibroadenoma”:
• Cysts larger than 0.3cm
• Sclerosing adenosis
• Epithelial calcifications
• Papillary apocrine change
• Juvenile fibroadenoma:
• Increased stromal cellularity
• Fascicular stromal arrangement
• Pericanalicular epithelial growth pattern
• UDH with often delicate micropapillary epithelial projections (“gynaecomastoid”-like)

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

• no consistent cytogenetic changes

Other features:

• most common benign breast tumour
• hormonally responsive epithelium
• may increase in size or infarct during pregnancy
• no increased risk of subsequent breast CA
• “complex fibroadenoma”
• “proliferative changes without atypia” group of cancer risk
• Mild increase in risk

References:

• Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004.
• Lakhani SR et al. eds. WHO Classification of Tumours of the Breast, 4^th ed. (2012)
• Juvenile fibroadenoma section only