Extramammary Paget Disease
Supplemental Studies
Immunohistology
- Markers useful for separating Paget disease from other processes
- CK7 is the most useful marker as it is not expressed by the surrounding epidermal cells
- Normal Toker cells and Merkel cells are positive for CK7 and must be distinguished morphologically
- CAM5.2 may be useful as a substitute as it is nearly as specific
- Other anti-keratins and EMA will stain most Paget cells but are not as specific
- BerEp4 has been proposed as a useful marker
- Extramammary Paget disease is 100%
- Squamous cell carcinoma in situ is negative
- One report, needs confirmation
- High molecular weight cytokeratin (HMWCK) and p63 are useful complementary markers
- Squamous carcinoma in situ is nearly always positive while Paget cells are nearly always negative
- S100 may be expressed by Paget cells so it is not a perfect marker to rule out melanoma
- MelanA is better
- CK7 is the most useful marker as it is not expressed by the surrounding epidermal cells
- Markers useful for separating primary from secondary Paget disease
- GCDFP15 (BRST2) and CK20 are useful for separating primary from secondary Paget disease
- In secondary Paget disease the phenotype may depend upon the nature of the underlying carcinoma
- Most cases with underlying rectal adenocarcinoma are reported to be CK7+20+, even though 90% of rectal adenocarcinomas are CK7-20+
Primary Paget Disease Secondary Paget Disease GCDFP15
90% 7% CK7
100% 70% CK20
12% >95% HMWCK
0% See note p63
0% See note CDX2
0% See note - The phenotype of secondary Paget disease is variable, depending upon the nature of the underlying carcinoma
- Rectal adenocarcinoma is CK7 variable, CK20+, CDX2+, p63-
- Urothelial carcinoma is usually CK7+, CK20+, CDX2-, p63+
