Pathways of vulvar intraepithelial neoplasia and squamous cell carcinoma

Vulvar squamous cell carcinoma (VSCC) accounts for >90% of the malignant tumours of the vulva. Most VSCCs originate in intraepithelial lesions, named vulvar intraepithelial neoplasia (VIN), that precede the development of VSCC by a variable period of time. Strong evidence has accumulated showing that there are two different aetiopathogenic pathways for the development of VSCC and VIN, one associated with infection by human papillomavirus (HPV), and a second independent of HPV infection. These two different types of VSCC have different epidemiological, pathological and clinical characteristics, and should therefore be considered as two separate entities. Histologically, HPV‐associated VSCCs are of the basaloid or warty type, and arise from VIN of the usual type. Inactivation of p53 and the retinoblastoma tumour suppressor gene product by the viral gene products E6 and E7 is involved in the process of malignant transformation. HPV‐independent VSCCs are histologically keratinizing, are associated with differentiated VIN and lichen sclerosus, and frequently show mutations of p53. p16^INK4a and p53 immunostaining can be useful for classifying VSCC into HPV‐associated or HPV‐independent. Although large, multicentre studies are needed to definitively assess the involvement of HPV in the prognosis of VSCC, most studies have not found clear differences in survival between HPV‐associated and HPV‐independent tumours.     

Presence and type of oncogenic human papillomavirus in classic and in differentiated vulvar intraepithelial neoplasia and keratinizing vulvar squamous cell carcinoma

The presence and type of oncogenic papillomavirus (HPV) in classic warty/basaloid vulvar intraepithelial neoplasia and in differentiated vulvar intraepithelial neoplasia and keratinizing vulvar squamous cell carcinoma was investigated using three techniques, that is, histology, in situ hybridization, and PCR-ELISA. HPV typing was performed using in situ hybridization and PCR-ELISA. Differentiated vulvar intraepithelial neoplasia and invasive keratinizing vulvar squamous cell carcinoma proved completely negative for HPV by PCR-ELISA, in situ hybridization, and histologic examination, while in classic vulvar intraepithelial neoplasia, a HPV positivity of 66.1% was found. HPV 16 was the predominant type, with HPV 35, 33, and 52 types found rarely and sometimes together with HPV 16. PCR-ELISA proved to be the most suitable method to detect and type mucosal oncogenic HPVs. The absolute absence of HPV DNA in differentiated vulvar intraepithelial neoplasias and in keratinizing vulvar squamous cell carcinoma suggests a strong HPV-independent pathway of malignant progression to invasive carcinoma.     

Premalignant and malignant squamous lesions of the vulva

Vulvar premalignant squamous lesions include low- and high-grade intraepithelial neoplasias. High-grade lesions include usual (classic) and differentiated (simplex) vulvar intraepithelial neoplasia (VIN). Usual VIN (uVIN), the most common, is related to human papilloma virus (HPV), occurs in younger patients, and is frequently multifocal. Differentiated VIN (dVIN), less common, is related to lichen sclerosus and other chronic vulvar dermatoses, occurs in older women, and is usually unifocal. Terminology schemes for premalignant lesions are reviewed. Invasive squamous cell carcinoma also occurs in two distinct clinicopathologic settings. Most conventional keratinizing squamous cell carcinomas arise from a background of dVIN and comprise the majority of invasive squamous tumours. Warty and basaloid invasive squamous cell carcinomas likely develop from uVIN and comprise a minority of invasive tumours. Clinical features, microscopic findings, differential diagnoses, immunoprofiles, prognosis and treatment of premalignant and malignant lesions are addressed.     

Premalignant and malignant squamous lesions of the vulva

Vulvar premalignant squamous lesions include low- and high-grade intraepithelial neoplasias. High-grade lesions include classic (usual) and differentiated (simplex) vulvar intraepithelial neoplasia (VIN). Classic VIN (cVIN), the most common, is related to human papilloma virus (HPV), occurs in younger patients, and is frequently multifocal. Differentiated VIN (dVIN), less common, is related to lichen sclerosus and other chronic vulvar dermatoses, occurs in older women, and is usually unifocal. Terminology schemes for premalignant lesions are reviewed. Invasive squamous cell carcinoma also occurs in two distinct clinicopathologic settings. Most conventional keratinizing squamous cell carcinomas arise from a background of dVIN and comprise the majority of invasive squamous tumours. Warty and basaloid invasive squamous cell carcinomas likely develop from cVIN and comprise a minority of invasive tumours. Clinical features, microscopic findings, differential diagnoses, immunoprofile, prognosis and treatment of premalignant and malignant lesions are addressed.     

Prevalence of mucosal and cutaneous human papillomaviruses in different histologic subtypes of vulvar carcinoma.

Two independent pathways of vulvar carcinogenesis have currently been identified, one related to infection with mucosal human papillomaviruses (HPVs) and a second related to chronic inflammatory or autoimmune processes. The goal of the study was to examine a possible role of cutaneous HPVs from the beta genus in vulvar carcinogenesis and to evaluate the distribution of intratypic variants of HPV 16 in HPV 16-positive vulvar cancer. Consecutive cases of vulvar carcinoma were retrieved from the files and included the following histologic subtypes: keratinizing (n=21), basaloid (n=7), warty (n=1), mixed basaloid-warty (n=4), verrucous (n=4), keratoacanthoma (n=1), basal cell carcinoma (n=1). All tumors were microdissected and tested for 25 beta HPV types and 25 mucosal HPV types. Cases identified as positive for HPV 16 were further tested for intratypic variants. All cases were immunostained for p16INK4a. Beta HPVs were not detected in any of the tumor cases. Mucosal HPVs were detected in all but one basaloid/warty carcinomas; of these, nine cases (82%) were positive for HPV 16, including five European subtypes, one African subtype, one North American subtype and two indeterminate subtypes. Two of four verrucous carcinomas were positive for HPV 6. Mucosal HPVs were not detected in keratinizing carcinomas, keratoacanthoma and basal cell carcinoma. All cases of basaloid/warty carcinomas, but none of the remaining tumors, overexpressed p16INK4a protein. Our data do not support a role of beta HPVs in the pathogenesis of vulvar carcinoma. The study reaffirms the role of mucosal HPVs, in particular that of HPV 16, in the pathogenesis of basaloid and warty tumor subtypes. The HPV 16 intratypic variation showed correlation with patients' ethnic background. P16INK4a immunostaining seems to be a sensitive and specific marker of vulvar carcinomas positive for oncogenic mucosal HPVs.     

Histologic classification of penile intraepithelial neoplasia

Penile squamous cell carcinomas (SCCs) and their corresponding precancerous lesions can be classified in 2 major groups: human papillomavirus (HPV) related and HPV unrelated. In the former (warty and basaloid SCC), there is a predominance of undifferentiated basaloid cells. In the latter (eg, usual, papillary, and verrucous SCC), the predominant cell is larger with abundant eosinophilic cytoplasm. Based on these morphologic features, a new term, "penile intraepithelial neoplasia" (PeIN), was proposed. PeIN was further subclassified into differentiated and undifferentiated, with the latter being subdivided into basaloid, warty, and warty-basaloid subtypes. Macroscopically, PeIN subtypes are indistinguishable. Microscopically, differentiated PeIN is characterized by acanthosis, parakeratosis, enlarged keratinocytes with abundant "pink" cytoplasm (abnormal maturation), and hyperchromatic cells in the basal layer. In basaloid PeIN the epithelium is replaced by a monotonous population of uniform, small, round, and basophilic cells. Warty PeIN is characterized by a spiky surface, prominent atypical parakeratosis, and pleomorphic koilocytosis. Warty-basaloid PeIN show features of both warty and basaloid PeIN. There is a significant association of subtypes of PeIN with specific variants of invasive SCCs. This is a simple and reproducible nomenclature for penile precancerous lesions based on cell type and differentiation. It takes into account the similarities between vulvar and penile pathology and the hypothesis of a bimodal pathway of penile cancer progression.     

Characteristics of vulvar squamous cell carcinoma in Japanese women

Although the presence of racial differences in vulvar squamous cell carcinomas has been suggested, fully analyzed data concerning such tumors in Japanese women have not been reported. A total of 21 vulvar squamous cell carcinomas of Japanese women who lived in north-east Japan, were studied with respect to histological subtype, HPV, p53 and p16(INK4a). The majority of tumors consisted of keratinizing and non-keratinizing types (16/21, 76%), all of which were negative for HPV. The remaining five tumors of basaloid, warty or verrucous types were positive for HPV. HPV-negative tumors showed a trend of greater accumulation of gene abnormalities, including p53 gene mutation, than HPV-positive ones. p16(INK4a) overexpression was shown to not always be a marker for vulvar squamous cell carcinoma in Japanese women with activated high-risk HPV.     

Small vulvar squamous cell carcinomas and adjacent tissues. A morphologic study

Vulvar squamous cell carcinomas are of different subtypes and degrees of differentiation, and may be associated with adjacent lichen sclerosus and/or varying degrees of dysplasia. The aim of this investigation was to study small carcinomas with a diameter of less than 2 cm in order to find a possible relation between subtypes of carcinomas and adjacent epithelial changes. Fourteen cases of small vulvar squamous cell carcinomas were totally embedded in paraffin. Serial sectioning made a detailed mapping of all different lesions possible, and a two- and three-dimensional imaging was obtained in each case. Seven patients with keratinizing squamous cell carcinomas (median age 65) had adjacent lichen sclerosus. All carcinomas were completely surrounded by areas of VIN1. VIN2 and VIN3 were not found. Seven patients without lichen sclerosus (median age 58) showed squamous cell carcinomas of the keratinizing type (n=2) or the basaloid type (n=5). Five of these cases were incompletely surrounded by varying degrees of dysplasia, mainly VIN2 and VIN3. Two different pathogenetic pathways for the development of vulvar squamous cell carcinoma are likely.     

Analysis of clonality and HPV infection in benign, hyperplastic, premalignant, and malignant lesions of the vulvar mucosa

To elucidate the pathogenesis of vulvar carcinomas, we studied clonality and human papillomavirus (HPV) infection in vulvar epithelial diseases. Monoclonal composition was demonstrated in all 9 invasive tumors (squamous cell carcinoma [SCC], 6; basal cell carcinoma, 1; malignant melanoma, 2), 15 of 20 cases of vulvar intraepithelial neoplasia (VIN), 7 of 9 cases of Paget disease, 2 of 6 cases of lichen sclerosus (LS), and 2 of 3 cases of squamous cell hyperplasia (SCH); high-risk type HPV was revealed in 5 of 6 SCCs and 17 of 20 VINs. These observations might imply that a subset of cases of LS and SCH result from a neoplastic proliferation, similar to VINs but not related to infection with high-risk type HPV. In 1 case of SCC with concurrent VIN 3 in an adjacent lesion, both lesions showed the same pattern of X chromosome inactivation and the presence of HPV-16 in episomal and integrated forms, suggesting that monoclonal expansion triggered by high-risk type HPV integration is an early event for carcinogenesis of HPV-associated SCC.     

HPV-assoziierte Ver?nderungen an Vulva und Vagina

Non-neoplastic HPV-induced alterations of the vulva and vagina are frequent. The traditional three-tier grading system of vulvar intraepithelial neoplasia (VIN) will be replaced by the definition of usual and simplex type of VIN. The usual type is characterized by a strong association to high-risk HPV infections, the occurrence at younger age and multifocality, mostly associated with non-keratinizing squamous cell carcinoma. The differentiated (or simplex) type is rare and shows an association to older age and p53 alterations and is typically diagnosed co-incidentally with keratinizing squamous cell carcinoma. Vaginal intraepithelial neoplasia (VAIN) is still graded into VAIN 1-3 where VAIN?1 and 2 are mostly associated with low-risk HPV infections and a high spontaneous regression rate whereas VAIN 3 represents a high-risk HPV-associated lesion with capable progression into (micro-)invasive carcinoma. The differential diagnosis between a non-neoplastic condylomatous lesion and VIN common type and VAIN may be aided by p16 immunohistochemistry. The HPV-associated invasive vulvo-vaginal cancers are verrucous carcinoma (low-risk HPV) and the high-risk HPV-induced (non-keratinizing) squamous cell carcinoma (NOS), the condylomatous (warty) carcinoma and the very rare vaginal squamo-transitional carcinoma.     

Role of human papillomavirus in penile cancer,penile intraepithelial squamous cell neoplasias and in genital warts

Using PCR, the overall prevalence of human papillomavirus (HPV) DNA in penile carcinoma is about 40–45%, which is similar to the detection rate of HPV-DNA in vulvar carcinoma (50%). In analogy to vulvar cancer two different pathways of penile carcinogenesis seem to exist. In contrast to basaloid and warty penile cancers which are regularly HPV-associated (about 80–100%), only a part of keratinizing and verrucous penile carcinomas appear to be related with HPV (33–35%). Penile intraepithelial neoplasias comprising Bowen's disease, erythroplasia of Queyrat and bowenoid papulosis are precursor lesions of basaloid and warty carcinomas of the penis.Precursors of keratinizing carcinomas and verrucous carcinomas are not established. Whether lichen sclerosus and squamous-cell hyperplasia precede penile keratinizing carcinoma is a matter of discussion. Giant condylomata acuminata may precede the development of verrucous carcinomas in some cases. Since high risk HPVs are more frequently found in verrucous carcinomas than in giant condylomas, HPV typing may be a helpful diagnostic step to differentiate giant condyloma from verrucous carcinoma.     

Vulvar keratinizing squamous cell carcinoma in a 26-year-old woman

A 26-year-old Hispanic woman complaining of "itching" and "herpetic lesions" on the vulva for 9 months was seen at a university hospital. On physical examination, multiple vulvar masses were noted. Biopsies taken from these lesions showed invasive keratinizing squamous cell carcinoma. The vulvectomy specimen revealed 4 tumor masses, the largest located on the mons pubis. Although the incidence of vulvar intraepithelial neoplasia has increased in recent years, only very few cases of invasive carcinoma have been reported in young women. The tumors that occur at a younger age characteristically have basaloid or warty histology, in contrast to those occurring in older women, which usually are well-differentiated keratinizing carcinomas. We believe this is an unusual case of vulvar squamous cell carcinoma. In addition to our patient's young age, her tumor had a histologic profile usually found in lesions of an elderly woman. The tumor was negative for human papillomavirus by polymerase chain reaction analysis and was positive for p53 by immunohistochemistry.     

Chromosome 17 aneusomy detected by fluorescence in situ hybridization in vulvar squamous cell carcinomas and synchronous vulvar skin

Vulvar squamous cell carcinoma (SCC) affects a spectrum of women with granulomatous vulvar diseases, human papillomavirus (HPV) infections, and chronic inflammatory vulvar dermatoses. To determine whether there is evidence of chromosomal instability occurring in synchronous skin surrounding vulvar SCCs, we investigated abnormalities in chromosome 17 copy number. Samples of SCC, vulvar intraepithelial neoplasia (VIN), and surrounding vulvar skin were obtained from all vulvar excisions performed for squamous neoplasia at Albany Medical College from 1996 to 1997. Histological categorization, fluorescent in situ hybridization (FISH) for the alpha satellite region of chromosome 17, DNA content by image analysis, and Ki-67 labeling were evaluated. Controls of normal vulvar skin not associated with cancer were used for comparison. One hundred ten specimens were obtained from 33 patients with either SCC or VIN 3 and consisted of 49 neoplastic, 52 nonneoplastic, and 9 histologically normal vulvar skin samples. The majority of SCCs (88%) and a minority (18%) of VIN 3 excisions were associated with lichen sclerosus. Normal vulvar skin controls did not exhibit chromosome 17 polysomy (cells with more than four FISH signals), whereas 56% of normal vulvar skin associated with cancer did. Moreover, the frequency of polysomy significantly increased as the histological classification progressed from normal to inflammatory to neoplastic lesions. The largest mean value and variance for chromosome 17 copy number was identified in SCCs (2.4 +/- 1.0) with intermediate values identified, in decreasing order, for SCC in situ (2.1 +/- 1.0), VIN 2 (2.1 +/- 0.8), lichen sclerosus (2.0 +/- 0.5), lichen simplex chronicus (1.9 +/- 0.4), and normal skin associated with SCC (1.8 +/- 0.4) compared with control vulvar skin (1.5 +/- 0. 05). Concordance of chromosome 17 aneusomy between cancers and synchronous skin lesions was found in 48% of patients. Loss of chromosome 17 was identified 5% of all samples and was significantly associated with women with SCC in situ (HPV-related). Both DNA content and Ki-67 labeling positively and significantly correlated with mean chromosome 17 copy number (r = 0.1, P: = 0.007). A high degree of genetic instability (aneuploidy) occurs in the skin surrounding vulvar carcinomas. As these events could be detected in histologically normal skin and inflammatory lesions (lichen sclerosus), chromosomal abnormalities may be a driving force in the early stages of carcinogenesis. Differences in chromosomal patterns (loss or gain) support the concept of at least two pathways in vulvar carcinogenesis.     

Collagenase-3 (MMP-13) is expressed by tumor cells in invasive vulvar squamous cell carcinomas

Collagenase-3 (MMP-13) is a human matrix metalloproteinase specifically expressed by invading tumor cells in squamous cell carcinomas (SCCs) of the head and neck. Here, we have further elucidated the role of MMP-13 in tumor invasion by examining its expression in invasive malignant tumors of the female genital tract. Using in situ hybridization, expression of MMP-13 mRNA was detected in 9 of 12 vulvar SCCs, primarily in tumor cells, but not in intact vulvar epithelium, in cervical SCCs (n = 12), or in endometrial (n = 11) or ovarian adenocarcinomas (n = 8). MMP-13 expression was especially abundant in vulvar carcinomas showing metastasis to lymph nodes and was associated with expression of membrane type 1 MMP by tumor cells and gelatinase-A (MMP-2) by stromal cells, as detected by immunohistochemistry. MMP-13 mRNAs were detected in 9 of 11 cell lines established from vulvar carcinomas and in 4 of 6 cell lines from cervical carcinomas, whereas endometrial (n = 10) and ovarian (n = 9) carcinoma cell lines were negative for MMP-13 mRNA. No correlation was detected between MMP-13 expression and p53 gene mutations in vulvar SCC cell lines. However, MMP-13 expression was detected in 5 of 6 vulvar and cervical SCC cell lines harboring HPV 16 or 68 DNA. These results show that MMP-13 is specifically expressed by malignantly transformed squamous epithelial cells, including vulvar SCC cells, and appears to serve as a marker for their invasive capacity.     

Human papillomavirus genotyping by oligonucleotide microarray and p16 expression in uterine cervical intraepithelial neoplasm and in invasive carcinoma in Korean women

For evaluating the diagnostic significance of p16(INK4A) over-expression in the uterine cervical intraepithelial neoplasm and in invasive carcinoma, human papillomavirus (HPV) was detected and genotyped by oligonucleotide microarray in archival tissues of 117 cervical specimens, including 47 invasive squamous cell carcinomas (SCC), 30 cases of cervical intraepithelial neoplasia (CIN), 20 adenocarcinomas, and 20 cases of non-neoplastic cervix. The expression of p16(INK4A) protein was immunohistochemically studied in these cases and in five HPV-positive and one HPV-negative cervical cancer cell lines. HPV was detected in 50% of CIN, 61.7% of SCC, and 45.5% of adenocarcinomas. p16(INK4A) expression was seen in all 20 cases of adenocarcinoma, 78.7% (37/47) of SCC, and 96.7% (29/30) of CIN, but not in any cases of the non-neoplastic cervix. There was no difference in p16(INK4A) expression between the HPV-positive and HPV-negative cervical lesions. All HPV-positive and -negative cervical cancer cell lines expressed p16(INK4A) protein. In conclusion, the presence of p16(INK4A) expression in cervical squamous and glandular epithelium indicates the existence of dysplasia or malignancy in the uterine cervix, regardless of HPV infection.     

Primary squamous cell carcinoma of the vagina: human papillomavirus detection, p16(INK4A) overexpression and clinicopathological correlations

Fuste V, del Pino M, Perez A, Garcia A, Torne A, Pahisa J & Ordi J
(2010) Histopathology 57, 907–916 Primary squamous cell carcinoma of the vagina: human papillomavirus detection, p16 ^INK4A overexpression and clinicopathological correlations Aim: To determine the role of human papillomavirus (HPV) in the pathogenesis of primary squamous cell carcinoma of the vagina (SCCVa), and to evaluate its clinicopathological significance. Methods and results: All cases of SCCVa diagnosed over a 15‐year period from two hospitals in Barcelona, Spain (n = 32) were retrieved. Patients with a history of carcinoma of the cervix diagnosed <5 years before were excluded. HPV was detected and typed by polymerase chain reaction (PCR) using SPF10 primers. Immunohistochemistry was performed for p16 and p53. HPV was detected in 25 cases (78.1%). HPV16 was the most prevalent type. Patients with HPV‐positive tumours were associated frequently with a history of carcinoma or intraepithelial neoplasia of the cervix or vulva diagnosed more than 5 years before (56% versus 0%; P = 0.01). HPV‐positive tumours were more frequently of non‐keratinizing, basaloid or warty type than HPV‐negative neoplasms (84% versus 14.3%; P < 0.001), and showed diffuse positive immunoreactivity for p16^INK4a (96%, versus 14.3%; P < 0.001). The sensitivity and specificity of p16 to identify HPV‐positive tumours were 96% and 85.7%, respectively. Conclusions: A high number of SCCVs are related to HPV infection and may be identified by immunohistochemistry for p16. HPV‐positive tumours tend to affect women with history of cervical neoplasia.     

Distribution and characterization of subtypes of penile intraepithelial neoplasia and their association with invasive carcinomas: a pathological study of 139 lesions in 121 patients

We are presenting the morphological features of 121 cases of atypical penile intraepithelial lesions. The term penile intraepithelial neoplasia (PeIN) was used to encompass all of them, and lesions were classified into 2 major groups, differentiated and undifferentiated. The latter was further divided in warty, basaloid, and warty-basaloid subtypes. Ninety-five cases were associated with invasive squamous cell carcinomas. Differentiated lesions predominated (68%), followed by warty-basaloid (14%), basaloid (11%), and warty (7%) subtypes. Multifocality was found in 15% of the cases. Differentiated lesions were preferentially located in foreskin, whereas warty and/or basaloid subtypes were more prevalent in the glans. The former lesions were preferentially seen in association with keratinizing variants of squamous carcinoma, whereas the latter subtypes were found mostly in conjunction with invasive warty, basaloid, and warty-basaloid carcinomas. Lichen sclerosus was present in 51% of cases of differentiated lesions and absent in warty and/or basaloid subtypes. In summary, PeIN can be classified into 4 distinctive morphological subtypes. The proper pathological characterization of these lesions may provide important clues to the understanding of the pathogenesis and natural history of penile cancer.     

子宫颈病变中HPV L1蛋白和p16的表达

目的 研究HPV L1蛋白和p16在子宫颈各种病变中的表达情况,探讨它们在子宫颈病变进展中的预测价值.方法 应用免疫组化方法检测41例各种子宫颈病变(CIN1级18例、CIN2级9例、CIN3级8例和浸润性鳞状细胞癌6例)中HPV L1蛋白和p16的表达.结果 HPV L1蛋白在各种子宫颈病变中的阳性率为26.8%.其中HPV L1在CIN1中的阳性表达率为38.9%,CIN2为44.4%,CIN3和浸润性鳞状细胞癌均无表达.p16在各种子宫颈病变中的阳性率为68.3%,其在CIN1中的阳性表达率为38.9%,CIN2为77.8%,CIN3和浸润性鳞状细胞癌均表达阳性.100%CIN3和浸润性鳞状细胞癌为p16+/HPV L1-,而61.1% CIN1中为p16-/HPV L1+或p16-/HPV L1-.结论 随着子宫颈病变的进展,HPV L1阳性表达率降低而p16阳性表达率增高.p16+/HPV L1-提示子宫颈鳞状上皮内瘤变有进展的可能,而p16-/HPV L1+和p16-/HPV L1-可能为无进展的或潜在消退的子宫颈病变.     

Accentuated p53 staining in usual type vulvar dysplasia—A potential diagnostic pitfall

Evaluation of vulvar intraepithelial neoplasia (VIN) may be difficult due to overlapping histologic features seen in both usual (UVIN) and differentiated vulvar intraepithelial neoplasia (DVIN). DVIN represents a diagnostic challenge; poor inter-observer agreement is well documented. P53 has been described as a potentially helpful adjunct in some cases; however, intricacies in its interpretation remain. This study evaluated 41 consecutive cases which consisted of 23 keratinizing dysplasias that were morphologically suggestive of DVIN and 18 UVINs. All cases were stained with p16 and p53. Our results revealed that 22 of 41 (54%) VINs showed novel accentuated wild type (WT) staining with non-linear basal staining for p53, including 12 (52%) cases histologically suggestive of DVIN and 10 (56%) described as UVIN. P16 was positive in 100% of the accentuated wild type cases, consistent with a diagnosis of UVIN. Positive p53 and negative p16 staining was seen in 4 (17%) cases histologically suggestive of DVIN. Of these, 75% progressed to carcinoma, whereas only 1 of 35 (3%) patients with UVIN progressed to carcinoma. In conclusion, DVIN is difficult to diagnose due to potential histologic overlap with UVIN, especially the warty, or keratinizing, subtype. Accentuated WT p53 in absence of concurrent p16 staining may lead to misdiagnosis of DVIN, especially in small biopsy samples. P16/p53 staining should be performed in tandem with strict adherence to patterns considered positive, as patients with UVIN have significantly less risk of progression.