Surgical Pathology Criteria

Paget Disease of the Breast

Differential Diagnosis

Pagetoid Squamous Cell Carcinoma In Situ Mammary Paget Disease
Atypical cells usually merge with surrounding keratinocytes Discrete population of atypical cells
Atypical cells may keratinize Atypical cells may form lumens or be mucin positive
Desmosomes and keratohyaline granules may be visible in atypical cells Desmosomes and keratohyaline granules not present
HMWCK+, p63+, CK7 negative CK7 >95%+, p63 negative, HMWCK rare
GCDFP15 negative GCDFP15 50%+

 

Melanoma In Situ Mammary Paget Disease
Substantial proportion of atypical cells sit directly on the epidermal basement membrane Atypical cells at all levels but frequently have at least one layer of normal cells separating them from the basement membrane
No lumen formation or mucin positivity Atypical cells may form lumens or be mucin positive
CK7 and other keratins negative CK7 and other broad spectrum antikeratins >95%+
S100 nearly 100%+ S100 0-26%+
HMB45 and MelanA 60-95%+ HMB45 and MelanA negative
Rare cases of Paget disease are pigmented

 

Toker Cells Mammary Paget Disease
Small-medium sized bland cells Large atypical cells
No epidermal reaction Epidermis generally shows reactive changes
  • Both are CK7+
  • Both may show small lumens (less frequently with Toker cells)
  • Both have pale cytoplasm
  • Toker cells are normal inhabitants of the nipple epidermis (see Lundquist 1999)
  • Merkel cells may also be CK7+
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