Case 7 -

Vulvar Squamous Cell Carcinoma, Keratinizing Type, HPV Related Dr. Jaume Ordi, Hospital Clinic, Barcelona, Spain

Clinical History 27-year-old woman. 2 cm. vulvar exophytic tumor in the para clitoridal area. Case 7 - Figure 1 Click to view with ImageScope Click to view with a Web-Based Viewer Pathologic findings The histologic examination showed a conventional invasive well-differentiated keratinising squamous cell carcinoma. No intraepithelial component (VIN) was identified. Immunohistochemical stains showed an intense positivity for p16. p53 was negative in the tumor cells. High-risk HPV sequences (type 16) were identified using two different PCRs (GP5/GP6+ and SPF10). Diagnosis: Vulvar squamous cell carcinoma, keratinizing type, HPV related Discussion Invasive vulvar squamous cell carcinoma (VSCC) accounts for more than 90% of malignant vulvar neoplasms. Based on their etiopathogenesis, VSCCs have been divided into two groups with different clinical and pathological features. One group expresses sequences of high-risk human papillomavirus (HPV), whereas the other arises via independent-HPV pathways. The prognostic significance of these pathological groups is still controversial. Non-HPV-associated VSCCs, which account for two thirds of all VSCCs, arise in elderly women. Histologically, these lesions are of the conventional keratinizing type and are frequently associated with squamous cell hyperplasia and lichen sclerosus. In the last few years an infrequent variant of vulvar intraepithelial neoplasia (VIN), the differentiated (simplex) type of VIN, has been described in association with keratinizing VSCC. Non-HPV-associated VSCCs frequently show mutations of the tumor suppressor gene p53. As a consequence p53 protein is frequently detected immunohistochemically in keratinizing VSCC and differentiated (simplex) VIN3 due to cellular accumulation of the mutated abnormal protein. HPV-associated VSCCs account for approximately one third of all VSCCs. They are described as arising in young women and are frequently associated with synchronous or metachronous HPV-positive tumors of the uterine cervix, vagina or anus. HPV-associated VSCCs share risk factors with cervical carcinoma, such as cigarette smoking, condylomas, and multiple sexual partners. Histologically, HPV-associated VSCCs are of basaloid or warty type and arise from undifferentiated bowenoid or basaloid VIN. The malignant transformation is mediated by inactivation of p53 and retinoblastoma by the viral gene products E6 and E7. The inactivation of retinoblastoma results in an overexpression of p16. Molecular detection of HPV sequences has been used to define both subgroups of vulvar carcinomas and their precursors. Technical difficulties in routinely detecting and typing HPV in formalin-fixed, paraffin-embedded tissues prevents its widespread use in many laboratories. As a consequence, pure morphologic criteria are usually the only basis to classify HPV-positive and -negative VSCCs. However, there is increasing evidence that some overlap exists between morphological types of VSCCs in terms of their relationship to HPV. Thus, some conventional keratinizing VSCCs arising in young women are likely to be HPV-positive, while some HPV-negative VSCCs show verruciform or poorly differentiated areas that overlap with true warty or basaloid HPV-associated carcinomas. Recent results by our group show that, as observed in the uterine cervix, an intense and diffuse expression of p16 in a vulvar squamous cell carcinoma indicates a high-risk HPV-associated process, this being irrespective of the histological type. p16 expression is detected both in the infiltrative areas and in the associated intraepithelial lesions. Keratinizing VSCCs show, in contrast, a high frequency of p53 expression, which contrasts with the almost constant negativity in HPV-positive premalignant and malignant lesions. p16 and p53 tend to be mutually exclusive. In our series, the sensitivity and specificity of p16 immunostaining to detect HPV-associated carcinomas is higher than the sensitivity and specificity of histologic classification and those of p53 negative staining (Table 1). Thus, our results clearly indicate that p16 immunostaining can be a useful tool to properly classify VSCC into HPV-associated or non-HPV-associated. Table 1. Sensitivity, specificity, positive and negative predictive values for the diagnosis of human papillomavirus-associated carcinoma of diffuse positivity for p16, negative staining for p53 and basaloid or warty histology (from Santos et al, Am J Surg Pathol 2006; in press). p16 (+++) p53 (-) basaloid/warty histology Sensitivity 100% 93.8% 62.5% Specificity 98.7% 35.5% 93.4% Positive predictive value 94.1% 23.4% 66.7% Negative predictive value 100% 96.4% 92.2% A striking finding in our series was the overlap observed between the histological types and the association with HPV. Thus, more than one third of all HPV-positive VSCCs were of conventional keratinizing type, whereas a small, but significant number of HPV-negative VSCCs showed basaloid or warty features. This suggests that the proposed classification of VSCCs into basaloid, and warty, both considered to be associated with HPV infection, and keratinizing, considered not to be associated with HPV, has a limited reliability, and that histological analysis alone results in the misplacement of some tumors in terms of their HPV relationship. This overlapping may also reflect a certain degree of subjectivity in subclassifying the invasive component of VSCCs as referred by some authors. Thus, although basaloid and warty carcinomas can generally be readily distinguished from keratinizing squamous cell carcinomas or verrucous carcinomas, sometimes this distinction is difficult. These difficulties are particularly challenging in the proper diagnosis of warty carcinoma, which can closely mimic keratinizing or verrucous carcinoma, which is not related to HPV infection. Also, the presence of keratinization in basaloid carcinomas can hinder the differential diagnosis with poorly differentiated keratinizing squamous cell carcinomas. Moreover, some mixed basaloid-keratinizing squamous carcinomas that can pose serious problems have been described. p16 immunostaining may represent thus, a much more reliable tool in classifying VSCCs according to their relationship to HPV infection. References Al-Ghamdi A, Freedman D, Miller D, et al. Vulvar squamous cell carcinoma in young women: a clinicopathologic study of 21 cases. Gynecol Oncol. 2002; 84:94-101. Andersen WA, et al. Vulvar squamous cell carcinoma and papillomaviruses: two separate entities? Am J Obstet Gynecol. 1991; 165:329-335. Crum CP, et al. Pathobiology of vulvar squamous neoplasia. Curr Opin Obstet Gynecol. 1997; 9:63-69. Gualco M, et al. Morphologic and biologic studies on ten cases of verrucous carcinoma of the vulva supporting the theory of a discrete clinico-pathologic entity. 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