A panel of p16^INK4A, MIB1 and p53 proteins can distinguish between the 2 pathways leading to vulvar squamous cell carcinoma

Abstract

Two pathways leading to vulvar squamous cell carcinoma (SCC) exist. The expression of proliferation-and cell-cycle-related biomarkers and the presence of high-risk (hr) HPV might be helpful to distinguish the premalignancies in both pathways. Seventy-five differentiated vulvar intra-epithelial neoplasia (VIN)-lesions with adjacent SCC and 45 usual VIN-lesions (32 solitary and 13 with adjacent SCC) were selected, and tested for hr-HPV DNA, using a broad-spectrum HPV detection/genotyping assay (SPF 10 -LiPA), and the immunohistochemical expression of MIB1, p16 INK4A and p53. All differentiated VIN-lesions were hr-HPV-and p16-negative and in 96% MIB1-expression was confined to the parabasal layers. Eighty-four percent exhibited high p53 labeling indices, sometimes with parabasal extension. Eighty percent of all usual VIN-lesions were hr-HPV-positive, p16-positive, MIB1-positive and p53-negative. Five (of seven) HPV-negative usual VIN lesions, had an expression pattern like the other HPV-positive usual VIN lesions. In conclusion, both pathways leading to vulvar SCC have their own immunohistochemical profile, which can be used to distinguish the 2 types of VIN, but cannot explain differences in malignant potential. 1,2 Both types of vulvar cancer are preceded by their own type of vulvar intra-epithelial neoplasia (VIN). On the basis of histopathological characteristics, VIN lesions can be divided into usual VIN (also known as Bowenoid or classic VIN, basaloid or warty subtype) and differentiated VIN (formerly named simplex VIN or well-differentiated VIN).3 Recently, the International Society for Vulvovaginal Disease (ISSVD) has proposed a revised nomenclature for vulvar lesions. 2,3The majority of vulvar SCCs occur in elderly patients with lichen sclerosus and develops following an human papillomavirus (HPV)-negative pathway.4,5 Its premalignancy, differentiated VIN, can be difficult to distinguish from a benign vulvar lesion (e.g. chronic inflammation) or normal epithelium. 5,6 It is assumed that differentiated VIN is highly proliferative and might rapidly progress into an invasive neoplasm, because it is seldom found without (micro-invasive) vulvar carcinoma and often adjacent to HPV-negative vulvar SCC. 2,5,6 Since differentiated VIN is often unifocal and the amount of skin involved is limited, surgical treatment by means of a wide local excision probably reduces the risk of progression to invasive carcinoma. 7Usual VIN is often multifocal, occurs in younger women and is associated with smoking and HPV, predominantly HPV-16 and -18, and can lead to HPV-positive vulvar SCC. 8 One third of all vulvar SCCs is associated with HPV. 9 The risk of malignant transformation of usual VIN to an invasive carcinoma appears to be 3-4%. The viral gene products E6 and E7 interfere with 2 pathways of cell cycle regulation. HPV E6 can interact with p53, leading to p53 dysfunction, which allows for an absence of cell cycle arrest.6,10 HPV E7 can inactivate pRb which can result in an overexpression of p16 INK4A and hyperproliferation...

Patients with usual vulvar intraepithelial neoplasia-related vulvar cancer have an increased risk of cervical abnormalities

“…In general, several studies showed that patients with uVINrelated vulvar SCC are younger than dVIN/LS-related vulvar SCC patients (Hording et al, 1994;Hampl et al, 2006;Hoevenaars et al, 2008;van de Nieuwenhof et al, 2009a). In our study, we confirm this observation with a significant difference in age distribution between the two different groups, 72 years for the hrHPVunrelated and 54 years for the hrHPV-related groups (Po0.001).…”

Differentiated vulvar intraepithelial neoplasia is often found in lesions, previously diagnosed as lichen sclerosus, which have progressed to vulvar squamous cell carcinoma

“…8,12 In addition, despite the fact that differentiated VIN was first described in the 1960s by Abell 23 as a highly differentiated form of vulvar carcinoma in situ, until more recently, the entity has not gained wide attention because its existence as a clinicopathological entity has long been questioned. 18 As more insight is gained that vulvar squamous cell carcinomas originate from two different pathways, each with its own premalignant lesions, 24,25 differentiated VIN has been designated the direct precursor of the HPV-independent pathway. Earlier, all VIN lesions were classified as being HPV related, which explains the high incidence of lichen sclerosus with HPV-induced lesions, which turned out to be differentiated VIN instead of the nowadays socalled usual VIN lesions.…”

Phosphorylated S6 as an immunohistochemical biomarker of vulvar intraepithelial neoplasia

“…Full or near full thickness p16 INK4A immunostaining characterizes most classic VINs, but normal and hyperplastic vulvar epidermis, lichen sclerosus, and differentiated VIN are usually p16 negative. 17,18 Presence of strongly p53-positive suprabasal cells was proposed as an aid for the diagnosis of differentiated VIN 20 but this marker is not considered highly sensitive. Independent studies found a range of 54 to 83% of differentiated VINs to have abnormal p53 immunostaining patterns.…”

“…Independent studies found a range of 54 to 83% of differentiated VINs to have abnormal p53 immunostaining patterns. 9,17,20,37,38 The fact that p53 is detected only in some differentiated VIN lesions might be explained by differences in the type of TP53 gene mutation, with strong p53 immunostaining associated with dominant-negative missense mutations and absence of staining associated with TP53 deletions. 9 Weak basal layer p53 staining has been reported in some lichen simplex chronicus and lichen sclerosus lesions in the absence of basal atypia and not associated with carcinoma.…”

“…Immunohistochemical analysis for abnormal patterns of p16 INK4A , p53, and MIB1/Ki-67 expression, separately or as a panel, can distinguish classic from differentiated VIN but these markers often fail to identify the latter. [17][18][19][20] We therefore sought to find a more reliable biomarker for differentiated VIN.…”