ORF1p Is a Potential Novel Diagnostic Marker for Differentiated Vulvar Intraepithelial Neoplasia

Accurate diagnosis of differentiated vulvar intraepithelial neoplasia (dVIN) can be challenging as histomorphologic features may be subtle and overlap with nondysplastic lesions. In practice, aberrant p53 expression supports the diagnosis, but a substantial percentage retains wild-type p53. Recently, the retrotransposon long interspersed nuclear element 1 has been detected in distinct cancer types. We have now investigated the expression of the long interspersed nuclear element 1 encoded protein ORF1p in dysplastic and nondysplastic vulvar samples to assess its diagnostic value. Specimens of dVIN (n=29), high-grade squamous intraepithelial lesions (n=26), inflammatory vulvar lesions (n=20), lichen sclerosus (n=22), and normal vulvar epithelia (n=29) were included. ORF1p and p53 expression was determined using immunohistochemistry. The majority of dVIN [27/29 (93%)] and high-grade squamous intraepithelial lesions [20/26 (77%)] showed distinct (i.e. moderate or strong) ORF1p expression in the basal and suprabasal or all epithelial layers, respectively. Of note, ORF1p was present in all 4 cases of dVIN with wild-type p53 staining pattern. In contrast, ORF1p was negative or weakly expressed in most inflammatory lesions [14/20 (70%)] and lichen sclerosus [18/22 (82%), P <0.001]. Normal control epithelium exhibited negative staining in all cases. In conclusion, ORF1p might be a useful diagnostic marker for dVIN, especially in cases with retained wild-type p53.