Immunohistochemical staining for proliferating cell nuclear antigen, BCL2, and Ki-67 in vulvar tissues

Dysplastic cells of the uterine cervix commonly react with antibodies to Ki-67 and proliferating cell nuclear antigen (PCNA), but less is known regarding the reactivity of vulvar lesions. Paraffin-embedded slides from seven normal vulvar tissues, eight cases of lichen sclerosus, and 10 cases of vulvar intraepithelial neoplasia (VIN), many with associated condylomatous changes, were immunostained with antibodies to PCNA, Ki-67, and BCL2 protein, a protooncogene product normally expressed only in basal cells of squamous epithelium. Ki-67 and PCNA nuclear staining was largely restricted to basal and parabasal cells in normal tissues and lichen sclerosus. Focal midepithelial staining with PCNA and Ki-67 was seen in one case of lichen sclerosus; a vulvar biopsy of this patient 1 year later was negative for VIN. Both antibodies stained dysplastic cells at higher epithelial levels in VIN, but Ki-67 was more consistently reactive and showed a sharper distinction from adjacent histologically uninvolved epithelium compared to PCNA. Condylomatous changes were variably stained. The pattern of BCL2 staining was identical in normal vulva, lichen sclerosus, and VIN, but BCL2 decorated occasional mitotic figures in VIN. Overall, Ki-67 was a better marker of vulvar dysplasia than PCNA.