Extramammary Paget's disease may be classified into four subtypes based on site of origin and area affected.
Classification
The classification of extramammary Paget's disease is shown below in a tabular form:
Type of Extramammary Paget's Disease
Description
Vulval Extramammary Paget's Disease
The majority of cases of vulval extramammary Paget's disease are primary; that is, arising within the epidermis, and very few are associated with cutaneous sweat gland tumors.
In cases where there is a prominent dermal invasive component, it may be impossible to prove the primary site of origin of the tumor.
A new variant of “mammary like” cutaneous glands, which combines morphological features of eccrine, mammary, and apocrine glands, and occurs predominantly in the interlabial sulcus on the vulva, has also been proposed as the site of origin of sweat gland derived tumors from which extramammary Paget's disease arises.
Vulval extramammary Paget's disease has been described in association with endocervical, endometrial, vaginal, vulval (eg., Bartholin's gland), urethral, and bladder neoplasms.
This phenomenon of epidermal colonisation by cells from a neoplasm originating within local internal organs with epithelial linings contiguous with the affected skin is described in many articles as spread from “internal malignancy”.
Rare reports exist of extramammary Paget's disease associated with distant tumors arising in organs without a direct epithelial connection to the affected epidermis (ovarian carcinoma, hepatocellular carcinoma, bile duct carcinoma, and renal cell carcinoma).
Vulval extramammary Paget's disease has also been described in association with breast carcinoma. It is likely that such cases simply represent synchronous coincidental neoplasms. No evidence exists in any of the described cases that the Paget's cells originated from the internal malignancy.[1][2][3][4][5][6][7][8][9][10]
Axillary Extramammary Paget's Disease
Axillary extramammary Paget's disease may, arise within the epidermis or from neoplasms in the local apocrine glands, however exclusion of neoplastic disease in the breast tissue is mandatory before a diagnosis of primary extramammary Paget's disease is made in this site.
Analysis of c-erbB-2 expression may be of use in this differential diagnosis.
Perianal Extramammary Paget's Disease
Perianal extramammary Paget's disease is rare than vulval disease but is strongly associated with adenocarcinoma of the colorectum and anus.
Unlike vulval extramammary Paget's disease, approximately 70–80% of cases of perianal disease arise secondary to invasive malignancy in the rectum, anus, or colon.
Thorough investigation of perianal region is mandatory if a diagnosis of perianal Paget's disease is given.[11]
Paget's Disease of Male Genitalia
Disease of the male genitalia is thought to be more frequently associated with internal malignancy (eg., bladder, urethral, prostatic, and testicular neoplasms) than is vulval extramammary Paget's disease.[6][7][12]
Type of extramammary Paget's disease
Features
Useful markers
Primary (cutaneous origin)
Intraepithelial cutaneous Paget disease of the usual type
Intraepithelial cutaneous Paget disease with invasion
Intraepithelial cutaneous Paget disease as a manifestation of underlying adenocarcinoma of skin appendage