Extramammary Paget's Disease (EMPD) Classifications
How is EMPD Classified?
Extramammary Paget’s disease (EMPD) is often difficult to diagnose and is frequently present for many years before treatment begins. Once diagnosed, some pathologists will place an EMPD diagnosis within an EMPD classification. However, in some countries the diagnosis many be as straightforward as EMPD or invasive EMPD.
In 2002, Wilkinson and Brown proposed an extramammary Paget’s disease (EMPD) system of classification of either primary (cutaneous origin) or secondary (of non-cutaneous origin). The two EMPD classifications have three subtypes:
Primary EMPD (cutaneous origin)
A) Intraepithelial cutaneous EMPD of the usual type
B) Intraepithelial cutaneous EMPD with invasion
C) Intraepithelial cutaneous EMPD as a manifestation of underlying adenocarcinoma of skin appendage
Secondary EMPD (of non-cutaneous origin)
A) Anorectal origin
B) Urothelial origin
C) Other origin
In the United Kingdom, extramammary Paget’s disease (EMPD) is often classified into several subtypes:
Type 1a – Primary cutaneous extramammary Paget’s disease arising for apocrine glands within the epidermis (in situ) or underlying skin appendages.
Type 1b – Primary cutaneous extramammary Paget’s disease (15-25%) is associated with invasive Paget's disease or adenocarcinoma in situ.
Type 2 – Extramammary Paget’s disease originating from underlying anal or rectal adenocarcinoma.
Type 3 – Extramammary Paget’s disease originating from bladder adenocarcinoma.
Other physicians, in other regions, have used an EMPD classification system which has three levels:
In situ in the epidermis (IE)
Microinvasion into the papillary dermis (MI)
Deep invasion into the reticular dermis (DI)
All of these classification systems are used by some physicians, in some countries, but to date there is not a classification system universally accepted in all nations.