Usual Ductal Hyperplasia (UDH)

Intraductal hyperplasia

Epithelial hyperplasia

Usual hyperplasia

Epitheliosis

Hyperplasia without atypia

Epidemiology:

• 53 y average age

Common sites:

Gross features:

• Not grossly appreciable
• Microcalcifications occasionally

Histologic features:

• more than 2 cell layers in a duct or acinus
• may fill and distend the duct or acinus
• cells overlapping
• often includes both luminal and myoepithelial cells
• apocrine metaplastic epithelial cells sometimes
• foamy histiocytes maybe
• often irregular lumens/fenestrations at the periphery
• slit-like lumens
• nuclei parallel rather than perpendicular to the spaces
• haphazard orientation
• irregularly placed cells
• indistinct borders
• variably sized nuclei
• streaming or syncytial pattern often
• particularly in the centre of the proliferation
• stretched or twisted epithelial bridges
• calcifications sometimes
• nuclear grooves and intranuclear inclusions often
• micropapillary architecture occasionally
• broad base and a narrow or pinched tip
• hyperchromatic, almost pyknotic appearing nuclei
• necrosis rarely

Immunophenotype:

Marker:	Sensitivity:	Specificity:
ER/PR (variable staining)
HMWK (CK5/6 or 34betaE12)	50-80% strongly positive (heterogeneous or mosaic pattern)
LMWK

Molecular features:

• No consistent genetic alterations

Other features:

• Not considered to be a precursor lesion in most cases
• Slightly elevated risk for subsequent invasive carcinoma in either breast (1.5 to 2-fold)
• Should not alter the frequency of mammographic screening

References:

• Lakhani SR, Ellis IO, Schnitt SJ, Tan PH, van de Vijver MJ. (eds) WHO Classification of Tumours of the Breast (2012)