Carcinomas with Apocrine Differentiation

Apocrine Carcinoma

Epidemiology:

• Extensive apocrine differentiation is seen in ~4% of invasive breast carcinomas

Common sites:

Gross features:

Histologic features:

• Apocrine differentiation is commonly seen in invasive carcinoma NST, as well as some special types
• Apocrine differentiation is also seen in lobular carcinoma in situ and ductal carcinoma in situ.
• Enlarged nuclei with prominent nucleoli
• Cytoplasmic changes, either or combination of:
• Type A cells: abundant granular eosinophilic cytoplasm with PASD positivity
• Type B cells: abundant foamy cytoplasm

Immunophenotype:

Marker:	Sensitivity:	Specificity:
Androgen receptors
ER/PR (neg) (Note: a novel isoform ER-alpha36 has been shown to be frequently overexpressed)	usually
Bcl-2 (neg)	Typically
GCDFP-15	Typically (May be lost in advanced stage tumours)

Molecular features:

• “apocrine molecular signature (see WHO 2012)

Other features:

• No clear prognostic or predictive association
• “apocrine molecular signature” may be associated with poor prognosis

References:

• Lakhani SR et al. WHO Classification of Tumours of the Breast (2012)
• All except genetics sections