Extramammary Paget Disease
Definition
- Intraepithelial involvement of the skin by (non-squamous) carcinoma cells
Diagnostic Criteria
- Intraepithelial population of large atypical cells (Paget cells) distinct from surrounding normal epithelial cells
- Large nuclei, prominent nucleoli
- Abundant pale cytoplasm
- Scattered individually and in clusters
- May form small acini
- Lack features of squamous differentiation
- No visible intercellular bridges
- No transition to surrounding squamous cells
- Most cases mucin positive
- May form signet rings
- Underlying chronic inflammation common
- Epidermal hyperplasia and hyperkeratosis and parakeratosis frequently present
- Present in half of cases
- >90% of anal cases
- Three patterns described
- Squamous hyperplasia NOS
- May result in pseudoepitheliomatous hyperplasia
- Fibroepithelioma-like
- Anastomosing network of rete ridges
- Especially frequent in perianal cases
- Papillomatous
- HPV negative
- Paget cells may be shrunken and pyknotic
- Extramammary Paget disease can be separated into primary and secondary types
- Primary type not associated with underlying deep carcinoma
- Positive for GCDFP15 and negative for CK20 (see Supplemental Studies and Differential Diagnosis at left sidebar)
- Invasion is uncommon, but can occur
- Secondary type is associated with an underlying internal carcinoma
- Negative for GCDFP15 and frequently CK20 positive
- Phenotype may depend upon nature of underlying carcinoma
- Most common underlying carcinomas
- Rectal adenocarcinoma
- Urothelial (transitional cell) carcinoma
- Most common locations
- Vulva
- Anal/perianal
- Scrotum and penis
- Inguinal
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates : 10/7/10