GATA3 immunohistochemistry as a diagnostic adjunct for differentiated vulvar intraepithelial neoplasia: utility and limitations

Proficiency Testing of p53 Immunohistochemistry Pattern Read-out in Vulvar Biopsies Demonstrates Frequent Basal Overexpression Interpretation in TP53 Wild-type Cases

Recently, criteria for p53 immunohistochemistry (IHC) interpretation were described in squamous neoplasia of the vulva. This pattern-based approach detailed 2 wild-type patterns (scattered and basal-sparing) and 4 mutant patterns (parabasal/diffuse overexpression, basal overexpression, null, and cytoplasmic). However, the proficiency of pathologist read-out has not been studied. We created an online tool to evaluate p53 IHC interpretation proficiency. p53 IHC on 90 vulvar biopsies (n=31 squamous insitu/premalignant and n=59 benign lesions) were scanned (without corresponding H&E). Fifteen pathologists assessed 45 cases in Module A and assigned each case as wild-type or mutant via the 6 p53 IHC patterns. Following Module A, participants were given the suggested p53 IHC pattern and TP53 sequencing data for each case. After self-review, pathologists completed a second 45 case set (Module B). The average pathologist score per case increased from Module A to Module B (69.8%-87.7%, P=0.0005). Pathologist proficiency was excellent in the parabasal/diffuse (100%-100%), null (93.3%-90.0%), and basal-sparing (88.9%-100%) patterns. The greatest discrepancy was due to the interpretation of the basal overexpression pattern in cases that were TP53 wild-type by sequencing, but this improved with educational intervention. Scores for the scattered pattern improved from 64.9% to 82.8% and basal overexpression from 73.3% to 91.1% after completion of the training module. Pathologists should exhibit caution when interpreting p53 IHC as basal overexpression, as this pattern can be seen in the absence of TP53 alterations. There were 2 cases with convincing p53 IHC abnormal patterns (1 parabasal/diffuse and 1 null) without TP53 mutations by sequencing.

Verruciform Acanthotic Vulvar Intraepithelial Neoplasia Harbors Recurrent Genomic Alterations Found in HPV-independent Squamous Cell Carcinoma

The term verruciform acanthotic vulvar intraepithelial neoplasia (vaVIN) was coined to describe HPV-independent p53-wildtype lesions with characteristic clinicopathologic characteristics and association with vulvar squamous cell carcinoma (vSCC). We aimed to expand on the molecular landscape of vaVIN using comprehensive sequencing and copy number variation profiling. vaVIN diagnosis in institutional cases was confirmed by a second review, plus negative p16 and wildtype p53 by immunohistochemistry. Multigene next-generation sequencing and shallow-whole genome sequencing were used to survey for single-nucleotide variants (SNV), copy number alterations, and structural variants. Targeted TERT promoter sequencing was also carried out. Nineteen patients with vaVIN were included; 4 had concurrent vSCC. The median patient age was 74 (range 56-90) years. Genomic aberrations were noted in 18 cases (95%) as follows: PIK3CA in 10 (53%), CDKN2A in 7 (37%), HRAS in 6 (32%), FAT1 and NOTCH1-2 in 5 each (26%), TSC2 in 2 (11%), and PTEN, ARID2, and KRAS in 1 (5%) each. TERT promoter variants were detected in 11 of 13 cases successfully tested (85%). Five vaVINs harbored a TP53 variant but showed wild-type p53 immunohistochemical expression. In one of these, the concurrent carcinoma showed abnormal p53 and biallelic TP53 mutations. Out of 15 patients with follow-up (mean: 20, range: 2-50 mo), vaVIN persistence/recurrence was seen in 8 (53%), and subsequent vSCC in 2 (13%). At the last encounter, 3 (20%) patients had persistent disease and 1 (7%) died of vSCC. vaVIN is characterized by a wider molecular spectrum, beyond known alterations in PIK3CA, HRAS, and ARID2, to include TERT promoter, CDKN2A, FAT1, and NOTCH1-2, which are characteristic of HPV-independent vSCC. vaVIN can occur with concurrent or subsequent carcinoma, sometimes with fatal outcomes. These findings support the concept of vaVIN as a neoplastic process within the family of HPV-independent vulvar neoplasia.

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.

Gene of the month: GATA3

GATA binding protein 3 (GATA3) is a zinc-finger pioneer transcription factor involved in diverse processes. GATA3 regulates gene expression through binding nucleosomal DNA and facilitating chromatin remodelling. Post-translational modifications modulate its activity. During development, GATA3 plays a key role in cell differentiation. Mutations in GATA3 are linked to breast and bladder cancer. GATA3 expression is a feature of the luminal subtype of bladder cancer and has implications for immune status and therapeutic response. It also has clinical relevance in squamous cell carcinomas and soft tissue sarcomas. This paper reviews the structure and function of GATA3, its role in cancer and its use and pitfalls as an immunohistochemical marker.

GATA3 Expression in HPV-associated and HPV-independent Vulvar Squamous Cell Carcinomas: Patterns of Expression and Prognostic Significance

Substantial diminution or loss of GATA3 expression is reportedly frequent in human papillomavirus-independent (HPVI), p53-mediated vulvar intraepithelial neoplasia. Herein, we study GATA3 expression in vulvar squamous cell carcinoma (VSCC) and assess its clinicopathologic significance. Eighty-six cases of VSCC diagnosed at a single institution were immunohistochemically assessed for their expression of GATA3, as well as any possible relationships with patient outcomes and other clinicopathologic parameters. Given that GATA3 expression pattern in the normal vulvar epidermis is typically strong basal staining with a uniform upward extension until at least the mid epidermal layers, VSCCs were scored using a previously reported tripattern system: pattern 0 (>75% tumor staining), pattern 1 (25% to 75% staining), and pattern 2 (<25% staining). Severe loss of GATA3 expression (pattern 2) was present in both human papillomavirus-associated (HPVA) and HPVI VSCC but was significantly more common in HPVI cases ( P <0.001). Among 52 HPVA VSCCs, 16 (30.7%), 15 (28.8%), and 21 (40.3%) cases showed patterns 0, 1, 2 staining whereas among 34 HPVI VSCCs, the respective frequencies were 1 (2.9%), 5 (14.7%), and 28 (82.3%). None of the 30 p53 abnormal VSCCs showed pattern 0 staining (0%). Five (16.6%) and 25 (83.3%) showed patterns 1 and 2 staining, respectively. On univariate analysis, the pattern 2 cohort showed a significantly worse overall survival (OS) and disease-free survival (DFS) than the pattern 0 or 1 cohort ( P =0.011 and 0.024, respectively), but this finding was not independent of stage on multivariate analysis ( P =0.34; hazard ratio: 1.82; 95% CI: 0.55-6.06). Subgroup analysis of the p53 wild-type cases showed significantly worse OS for pattern 2 than the pattern 0 or 1 cohorts, independent of stage ( P =0.04; hazard ratio: 6.5; 95% CI: 1.08-39.8). Subgroup analysis of p53 abnormal cases, however, showed no difference in OS and DFS among the 3-tiered GATA3 cohorts. In summary, loss of GATA3 may be seen in both HPVA and HPVI VSCCs but is significantly more common in HPVI SCCs. Loss or substantial diminution of GATA3 expression (pattern 2) is a negative prognostic factor in vulvar SCCs, but only in the p53 wild-type subset, where its negative prognostic significance appears to be independent of stage.