Extramammary Paget Disease
Differential Diagnosis
| Pagetoid Squamous Cell Carcinoma In Situ / HSIL |
Extramammary 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 neg, BerEp4 neg |
CK7 >90%+, p63 & HMWCK neg (positive if underlying urothelial carcinoma), BerEp4+ |
| GCDFP15 neg |
GCDFP15 positive if primary, variable if secondary |
| Melanoma In Situ of the Anus |
Extramammary 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%+ |
| HMB45 and MelanA 60-95%+ |
HMB45 and MelanA negative |
Rare cases of Paget disease are pigmented
