Expression of CK17 and SOX2 in Vulvar Intraepithelial Neoplasia: A Comprehensive Analysis of 150 Vulvar Lesions.

Background: Recently, the immunohistochemical markers cytokeratin 17 (CK17) and SRY-box2 (SOX2) have been evaluated as adjuncts for the diagnosis of high-grade vulvar intraepithelial neoplasia (VIN). In the present study, the aim was to assess CK17 and SOX2 expression in VIN by studying 150 vulvar lesions, originally reported as high-grade VIN and to assess the diagnostic accuracy.

Methods: All slides (H&E, p16, p53, Ki-67, CK17, and SOX2 stains) were independently assessed by six pathologists and the final diagnosis was reached in consensus meetings, as follows: 46 human papillomavirus (HPV)-independent VIN (including 30 p53 mutant and 16 p53 wild-type lesions), 58 high-grade squamous intraepithelial lesions (HSILs), 4 low-grade SILs (LSILs), 37 non-dysplastic lesions, and 5 lesions where the histology was inconclusive.

Results: CK17 positivity was observed in 100% p53 wild-type HPV-independent VIN, compared to 73% p53 mutant HPV-independent VIN, 14% HSILs, 0% LSILs, and 24% non-dysplastic lesions. SOX2 positivity was observed in 13% p53 wild-type HPV-independent VIN, 43% p53 mutant HPV-independent VIN, 2% HSILs, 0% LSILs, and 3% non-dysplastic lesions. The highest diagnostic accuracy (89%) for HPV-independent VIN was obtained when combining p53 and CK17 immunohistochemistry. The addition of SOX2 did not further increase diagnostic accuracy.

Conclusion: To conclude, aside from p53, both CK17 and SOX2 can be of value for reaching an accurate diagnosis of HPV-independent VIN.