American Urological Association - Paget Disease
- Essentially an adenocarcinoma in situ involving the epidermis.
- Affects scrotal inguinal area with spread to penis (rare as only site).
- Classified as primary (cutaneous) or secondary (from an underlying malignancy).
- Clinical: 6th –7th decades, fairly rare, but most cases are associated with an underlying carcinoma (especially bladder, urethra, or prostate).
- Gross: Scaly erythematous or eczematous patches or plaques.
- Intraepithelial proliferation of large atypical cells with vacuolated cytoplasm and large vesicular nuclei (Paget cell) (image A) & (image B).
- Tumor cells proliferate within background normal epithelium.
- Atypical cells tend to cluster at the tips of the rete pegs.
- Intracytoplasmic mucin vacuoles may be demonstrated by a PAS or mucicarmine stain.
- Primary Paget disease confined to epidermis has good prognosis if completely excised; outcome of secondary Paget disease depends on underlying cause.
- Primary Paget disease: CK7+/CK20-.
- Secondary Paget disease: Related to underlying cause – urothelial CK7+/CK20+, anorectal carcinomas CK20+, CDX2+.
- DDX: (Tumor with similar intraepithelial spread or "pagetoid" growth)
- Melanoma, superficial spreading: melanin pigment; express melanoma markers S100, HMB-45 or MART1; mucicarmine -; CK7 and CK20-.
- Squamous cell carcinoma in situ with pagetoid growth: intercellular bridges; p63+, CK7 and CK20-.