Reply to Comment on HPV-independent, p53-Wild-type Vulvar Intraepithelial Neoplasia: A Review of Nomenclature and the Journey to Characterize Acanthotic Precursor Lesions of the Vulva

Precancerous Lesions of HPV-independent Vulvar Squamous Cell Carcinoma: Clinicopathologic Consideration of an Evolving Spectrum

HPV-independent squamous cell carcinomas of the vulva comprise the majority of vulvar cancers, but their putative precancers represent only a small proportion of the vulvar squamous intraepithelial lesions that are encountered in routine practice. The precancerous lesions of HPV-independent vulvar squamous cell carcinoma encompass a spectrum of lesions that, collectively, may pose significant diagnostic challenges. Included in this spectrum are differentiated vulvar intraepithelial neoplasia [dVIN], the prototypical lesion of the group, which is characterized by a high propensity for progression, a relatively short duration to progression, frequent association with lichen sclerosus, and according to our review of the recent literature, TP53 /p53 aberration in 50% to 95% (mean 77.4%) of cases. Regarding the latter, some authors consider TP53 /p53 aberration to be a diagnostic requirement for dVIN, although this is controversial, as discussed further herein. Also included in the spectrum of lesions that are considered in this review are possibly related HPV-independent, p53-wild type lesions that have historically been reported as "vulvar acanthosis with altered differentiation" (VAAD), "differentiated exophytic vulvar intraepithelial lesion" (DEVIL), "verruciform lichen simplex chronicus" (vLSC), and which more recently, have collectively been described as "verruciform acanthotic vulvar intraepithelial neoplasia (vaVIN)" or "vulvar aberrant maturation (VAM)." In this review, we perform a comprehensive clinicopathologic review of putative precancerous lesions of HPV-independent squamous cell carcinomas of the vulva, with an emphasis on recent developments in terminology, practical diagnostic issues, biomarkers, and pathogenesis.

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.

The Spectrum of HPV-independent Penile Intraepithelial Neoplasia: A Proposal for Subclassification

Compared with vulva, precursor lesions of human papillomavirus (HPV)-independent invasive squamous cell carcinoma (SCC) of the penis are insufficiently characterized. We analyzed the histologic and immunohistochemical characteristics of 70 peritumoral precursor lesions and correlated them with the histology and mutational profile of the adjacent HPV-negative invasive penile SCC. Atypical basal keratinocyte proliferation with variously elongated epithelial rete with premature squamatiziation, but regular superficial cornification, termed differentiated penile intraepithelial neoplasia (d-PeIN), were identified adjacent to 42/70 (60%) SCC (36/42 keratinizing ( P <0.001); 3 papillary, and 1 each verrucous, clear cell, sarcomatoid SCC). d-PeIN were associated with chronic inflammatory dermatoses (32/42; P <0.001), p53 overexpression (26/42; P <0.001), and hotspot mutations in TP53 (32/42; P <0.001), CDKN2A (26/42; P <0.001) or both (21/42; P =0.003) in the adjacent SCC. Cytoplasmic p16 ink4a overexpression in 5/42 d-PeIN correlated with CDKN2A missense mutations in the adjacent SCC. In all, 21/70 (30%) cornified verrucous or glycogenated verruciform precursors with minimal atypia and wild-type p53 (18/21; P <0.001) occurred adjacent to verrucous or papillary SCC (17/21; P <0.001) and keratinizing (4/21) SCC, which harbored mutations in HRAS and/or PIK3CA (12/21; P <0.004). Undifferentiated p16 ink4a -negative full-thickness precursors were identified in 7/70 (10%) SCC. Four histologically different HPV-independent penile precursor lesions can be assigned to 2 major genetic/biological pathways with characteristic highly differentiated precursors requiring different clinical management decisions. These include d-PeIN in chronic inflammatory dermatoses, with p53 overexpression and TP53/CDKN2A mutations, and the p53 wild-type verrucous and verruciform precursors unassociated with dermatoses, but with mutations in oncogenes PIK3CA and HRAS .