American Urological Association - Paget Disease
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Paget Disease

Image A

Image B

  • 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.
  • Histology:
    • 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.
  • Immunohistochemistry:
    • 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-.