Immunohistochemistry of p63 in primary and secondary vulvar Paget's disease.

Vulvar Paget's disease (VPD) is classified into primary and secondary types. Differentiation of these subsets in biopsy specimen is important for appropriate therapy. Expression profile of cytokeratin (CK) 7 and CK20, gross cystic disease fluid protein-15 and uroplakin III has been reported as a differentiation marker of primary and secondary VPD. To examine the role of p63 immunostaining in differential diagnosis between primary VPD and VPD secondary to urothelial carcinoma (VPD-UC), expression of p63 was examined in nine cases of VPD. Paget cells in seven cases of VPD without UC did not express p63. In two cases of VPD associated with UC, Paget cells and UC cells had identical CK expression profile. UC cells were positive for p63 in both cases. In one case, Paget cells were positive for p63 and examination of the resected specimen showed that VPD was secondary to UC. In another case, Paget cells were negative for p63 and this was diagnosed as primary VPD independent of UC. This indicates that p63 is absent in Paget cells in primary VPD and is therefore useful in differentiating primary VPD from VPD-UC.