EMPD localised to the penis is extremely rare and only few cases have been reported. The first description of EMPD was by Crocker in 1889 when he reported a case affecting the penis and scrotum. EMPD is commoner in females and the elderly population, with a predilection for apocrine gland-bearing areas, most especially the vulva, perianal areas, axilla and penoscrotal region. Other sites reported include the groin, external auditory canal, chest and eyelids.
Clinically, presentation is often non-specific and can mimic any form of dermatosis. Differential diagnoses include Bowen's disease, tinea cruris, contact dermatitis, lichen simplex, lichen planus, psoriasis and seborrheic dermatitis. This can result in delayed presentation as was the case with our patient. In order to make the correct diagnosis, a high index of suspicion is required. The diagnosis is, however, made on histological grounds and supported by immunohistochemical analysis. Positive staining for CK7, a low molecular weight CK, in conjunction with immunonegativity for high molecular weight CKs, have consistently been proven to be the most useful diagnostic markers [2
]. This observation was confirmed in our case.
A recent classification based on the origin of the Paget's cells has been proposed by Wilkinson and Brown [3
]. They classified vulval Paget's disease (PD) into two broad groups – primary (of cutaneous origin) and secondary (of non-cutaneous origin). For primary PD, Type 1 is primary intraepithelial PD, Type 2 is primary intraepithelial PD with invasion and Type 3 is primary intraepithelial PD as a manifestation of underlying adenocarcinoma of skin appendage origin. Secondary PD originates from an underlying non-cutaneous neoplasm. This proposed classification could help decide on the extent of surgery, prevent unnecessary surgery and influence the outcome.
The true nature of EMPD and its relationship to underlying malignancy remains uncertain. Published reports suggest that up to 42% of patients have associated underlying secondary or non-cutaneous malignancy [4
]. However, there is a low incidence of internal malignancy with penoscrotal EMPD [5
]. The location of the internal malignancy appears to relate to the location of EMPD. Thus, penoscrotal and perianal locations are associated with adenocarcinoma of the genitourinary and digestive tracts, respectively [6
]. Siesling et al. found an increased risk of developing a second primary cancer in their series [7
]. Following diagnosis of EMPD, a thorough search for an underlying non-cutaneous malignancy is recommended [6
]. However, the decision and extent of the search should be tailored to the patient. Chiu et al. [9
] recommend screening for only those with perianal or invasive disease and young patients.
The treatment of choice is surgery with wide local excision and immediate reconstruction. Recurrence rates can be up to 60% [9
]. Results of frozen section-guided wide, local excision suggest a reduction in the recurrence rate to between 16% and 25% [9
]. However, the time constraints during surgery mean that assessment of the total margin status by frozen section is difficult and morbidity is likely to increase with prolonged anaesthetic times in frail, elderly patients. In their review, Zhu et al. [10
] found a 13% false negative frozen-section analysis. It is unlikely that rates can be reduced further, as positive margins in some cases are only diagnosed by immunohistochemistry. Other treatment modalities which have been used with mixed results include Mohs micrographic surgery, radiotherapy, Nd:YAG and carbon dioxide laser, topical Fluorouracil and 5% imiquimod cream.
The prognosis is good when the disease is confined to the epidermis. However, in the presence of dermal invasion, the prognosis is poor [10