Discussion:

Extramammary Paget Disease (EMPD) is the result of carcinoma cells within the epidermis having signs of glandular differentiation. The most common sites of EMPD in women are the labia majora and perianal region. Men most commonly develop the disease on the scrotum or perianal region (Goldblum et al., 2018).

Clinically the disease has an insidious onset, with the typical lesion being a scaly, erythematous plaque. This lesion can evolve over time into a nodule or ulcerate. Pruritus is the most common symptom patients experience; although some describe the lesion as painful rather than pruritic (Calonje et al., 2012).

The pathogenesis of EMPD is still unclear. Currently it is thought that EMPD can be categorized as primary or secondary disease. Primary disease represents a majority of cases, where the disease develops as the result of an in situ neoplasm originating from the intraepidermal sweat duct. Secondary disease represents EMPD developing in association with an underlying carcinoma (bladder, cervix, prostate, urethra, or rectum) with epidermotropic metastases (Calonje et al., 2012).

Microscopically both Paget Disease and EMPD are characterized by an intraepidermal expansion of atypical large cells with large nuclei. The cells characteristically have a pale vacuolated cytoplasm and vesicular nuclei. The background is typically a hyperkeratotic epidermis with parakeratosis and acanthosis. Paget cells contain mucopolysacchardies, which stain positive for PAS, mucicarmine, and alcian blue. CEA and CK7 IHC stains are positive in EMPD, with a negative staining pattern for CK20, S-100, and MelanA (Fletcher et al., 2013).

• Melanoma typically stains positively for MelanA and S-100. With negative staining for CEA (Fletcher et al., 2013).
• Pagetoid dyskeratosis is an incidental finding that stains negative for mucopolysacchardie stains and CEA. Cell atypia is also absent. (Calonje et al., 2012).
• Bowen Disease stains negative for CEA and S-100. CK7 staining is variable, with most cases staining negatively. Though two cases of CK7 positive Bowen Disease have been reported (Fletcher et al., 2013).

EMPD of the scrotum is a rare occurrence, most often presenting during the 6th or 7th decade of life (Fletcher et al., 2013).

Treatment for EMPD, regardless of location, is generally wide surgical excision with appropriate margins. However, local recurrence is common in EMPD. Penoscrotal disease has a reported 22% local recurrence rate (Calonje et al., 2012).