Table 1.

Immunohistochemistry in vulvar pre-invasive lesions

Lesion	Immunohistochemistry	Comment
VHSIL (VIN 2/3)	P16 block positivity, ki-67 extends above basal layers through entire epithelium	Ki-67 will stain above the basal layers in LSIL as well and cannot be used to distinguish LSIL from VHSIL. P16 is more useful in this distinction and can be occasionally positive in LSIL
dVIN	Aberrant p53 staining patterns. P16 not block positive. Ki-67 confined to basal layers	A panel of p53, p16, and ki-67 helpful in distinguishing VHSIL from dVIN
Vulvar Paget’s disease	Cells contain mucine (PAS-D or alcian blue), mucicarmine, CK 7, GCDFP-15, GATA377	Stains to distinguish secondary Paget’s disease of urothelial (including uroplakin200) or anorectal origin (including CDX-2, CK20201) should be considered in appropriate cases
Melanoma in situ	Positivity with s100, Melan-A, and HMB 45202	A panel to distinguish melanoma in situ from Paget’s disease can be helpful

dVIN, differentiated-type vulvar intraepithelial neoplasia; LSIL, low-grade squamous intraepithelial lesions; VHSIL, vulvar high-grade squamous intraepithelial lesions.