Diagnosis of verruciform acanthotic vulvar intra-epithelial neoplasia (vaVIN) using CK17, SOX2 and GATA3 immunohistochemistry.

AIMS:Verruciform acanthotic vulvar intra-epithelial neoplasia (vaVIN) is an HPV-independent, p53 wild-type lesion with distinct morphology and documented risk of recurrence and cancer progression. vaVIN is rare, and prospective distinction from non-neoplastic hyperplastic lesions can be difficult. CK17, SOX2 and GATA3 immunohistochemistry has emerging value in the diagnosis of HPV-independent lesions, particularly differentiated VIN. We aimed to test the combined value of these markers in the diagnosis of vaVIN versus its non-neoplastic differentials in the vulva. METHODS AND RESULTS:CK17, SOX2 and GATA3 immunohistochemistry was evaluated on 16 vaVINs and 34 mimickers (verruciform xanthoma, lichen simplex chronicus, lichen sclerosus, psoriasis, pseudo-epitheliomatous hyperplasia). CK17 was scored as 3+ = full-thickness, 2+ = partial-thickness, 1+ = patchy, 0 = absent; SOX2 as 3+ = strong staining ≥ 10% cells, 2+ = moderate, 1 + =weak, 0 = staining in < 10% cells; and GATA3 as pattern 0 = loss in < 25% basal cells, 1 = loss in 25-75% basal cells, 2 = loss in > 75% basal cells. For analysis, results were recorded as positive (CK17 = 3+, SOX2 = 3+, GATA3 = patterns 1/2) or negative (CK17 = 2+/1+/0, SOX2 = 2+/1+/0, GATA3 = pattern 0). CK17, SOX2 and GATA3 positivity was documented in 81, 75 and 58% vaVINs, respectively, versus 32, 17 and 22% of non-neoplastic mimickers, respectively; ≥ 2 marker positivity conferred 83 sensitivity, 88 specificity and 86% accuracy in vaVIN diagnosis. Compared to vaVIN, SOX2 and GATA3 were differentially expressed in lichen sclerosus, lichen simplex chronicus and pseudo-epitheliomatous hyperplasia, whereas CK17 was differentially expressed in verruciform xanthoma and adjacent normal mucosa. CONCLUSIONS:CK17, SOX2 and GATA3 can be useful in the diagnosis of vaVIN and its distinction from hyperplastic non-neoplastic vulvar lesions. Although CK17 has higher sensitivity, SOX2 and GATA3 are more specific, and the combination of all markers shows optimal diagnostic accuracy.