**4. HPV impact in squamous cell homeostasis**

entiated cells; grade III (Poorly differentiated) presenting <75% undifferentiated cells and grade IV (Anaplastic/Pleomorphic) >75% undifferentiated cells. Cell anaplasia degrees are also pointed as common approach to determine Penile Squamous Cell Carcinomas grading (Mikuz et al. 2004; Slaton et al. 2001), absence of anaplasia (well differentiated cells), grade 1; grade 2, moderately differentiated (<50% anaplastic cells); and grade 3, poorly differentiated (>50% anaplastic cells). Cubilla et al. (2009) reported a method to grade Penile Squamous Cell Carcinomas. Carcinomas with a minimal deviation from normal/hyperplastic morphology of squamous epithelium were considered Grade 1 (extremely well-differentiated). Grade 3 are tumors showing any proportion of anaplastic cells, identified as solid sheets or irregular small aggregates, cords or nests of cells with little or no keratinization, high nuclear cytoplasmic ratio, thick nuclear membrane, nuclear pleomorphism, clumped chromatin, prominent nucleoli and numerous mitosis. Grade 2 is composed by remainder tumors. Grading both

226 Human Papillomavirus and Related Diseases – From Bench to Bedside A Diagnostic and Preventive Perspective

In summary, Penile Squamous Cell Carcinomas represents an aggressive locoregional malignancy with dissemination process may occurring 20-40% (Guimarães et al. 2009), a lethal disorder that often presents after significant delay (Barocas & Chang 2010). Usually, death occurs within 2 years after initial diagnosis (Guimarães et al. 2009). Accurate evaluation of clinical stage, anatomical site, regional lymph nodes, and metastatic disease presents a pivotal

Papillomaviruses are a family of pathogens that infect exclusively the epithelial tissues of amphibians, reptiles, birds and mammals (Franceschi, 2005). The viruses are grouped accord‐ ing to the anatomic site of infection and their preference for either cutaneous or mucosal squamous epithelium. The cutaneous types, or beta papillomaviruses, are usually found in the general population and cause common warts. In contrast, the alpha, or mucosotropic, papil‐ lomaviruses have been implicated in mucosal infections (Snow & Laudadio, 2010; Vidal & Gillison, 2008). The mucosotropic group of human papillomavirus comprises 15 species and infects the anogenital tract, upper aerodigestive tract and other head and neck mucosa (Chow et al., 2010). Because they are sexually transmitted and play important roles in diseases, these viruses have received much attention and research and clinical investment (Chow et al., 2010). As molecular virology is depicted in details in another chapter, here we will only cover penile cancer-related aspects. Currently, over 200 HPV genotypes have been identified (Wang et al., 2012). HPVs with a high affinity for mucosal sites can be classified into non-oncogenic, or lowrisk, types or as potentially oncogenic, or high-risk, types. Mucosal and genital HPVs can be divided into low-risk (HPVs 6, 11, 40, 42, 43, 44, 54, 61, 70, 72, 81) and high-risk (HPVs 16, 18, 31, 33, 35, 51, 52) types according to their presence in malignant lesions (Bosch et al., 2002;

The multiplicity of functions of the small papillomavirus oncoproteins, E5, E6 and E7, continues to be studied through last decades, although there are several mechanisms well

role in treatment planning to predict the survival outcome (Barocas & Chang, 2010).

extremes of the spectrum is simple and reproducible.

**3. HPV**

Muñoz et al., 2003).

Different from other viruses, HPV does not infect or replicate in antigen-presenting cells (APCs) of the epithelium nor induce cell lysis, which is a key escape mechanism to avoid that APC recognize and produce antigens derived from the virion, and alerts immune system. About more than 50% of infections present seroconversion in the patients, but the production of antibodies usually occurs only months after the initial infection (Vidal & Gillison, 2008). The life cycle of papillomaviruses is closely tied to the epithelial differentiation process. Infection occurs exclusively in squamous epithelial cells with a preference for the keratinocyte stem cell as the initial target of HPV infection, which will allow the maintenance of viral replication (Vidal & Gillison, 2008). The route of entry for HPV infection is microtraumas or small wounds in the skin or mucosal surface, which are particularly important in penile HPV-infection. These breaks in the epithelial surface allow the virus to access and persist in the nuclei of infected basal layer cells of the epithelium. Until now, no single receptor has been definitively identified and established as being responsible for HPV entry, although is believed that receptors closely related to wound healing might be preferential targets for HPV infection, such as α6 integrin and glycosamioglycan heparin (Vidal & Gillison, 2008).

As most viruses, HPV uses the host cell DNA machinery to maintain the production of viral progeny. This mechanism of viral-induced cell growth is very well known and is analogous to other viruses that disrupt the control of cell growth (Hebner & Laimins, 2006). Following cell division, as the basal cells divide into squamous epithelial cells, HPV establishes its DNA genome in the host cell nuclei, replicates and reaches a high copy number. Infected cells then leave the basal layer, migrate toward the suprabasal regions and begin to differentiate. In the basal layer phase, the HPV genome is maintained at a low copy number, providing a type of stock of viral DNA for further use in cell divisions. At the same time, 'early' viral genes (E5, E6 and E7) are expressed, resulting in enhanced proliferation of the infected cells and their lateral expansion, working to spread infection cells throughout epithelial tissue. While the basal cells and viral DNA divide, some daughter cells may be maintained in the basal layers, whereas other daughter cells move toward the upper layers of the epithelium and begin to differentiate. During this process in which the infected cells enter into the suprabasal layers, the viral genome replicates to a higher copy number; 'late' viral gene (L1 and L2) expression is initiated; and structural proteins, as such capsid proteins, are formed. Subsequently, virions are assembled and released as the upper layer of epithelium is shed (Fehrmann & Laimins, 2003; Scheurer et al., 2005; Vidal & Gillison, 2008).

although it stills an important in penile pathogenesis. According to the current evidences, penile cancer can follow 2 distinct etiologic pathways: one is related to environmental factors, such as phimosis, smoking, poor personal hygiene and chronic inflammation; and other one is the HPV-related penile cancer (Rubin et al., 2001; Cubilla et al., 2010). Several studies have highlighted the prevalence of HPV infection in penile cancer, with an average prevalence of 47% to 48% in more than 60 studies (Backes et al., 2009; Miralles-Guri et al., 2009). Differently from cervix cancer, in penile cancer the prevalence of HPV infection varies according to histological subtypes, being strongly prevalent in basaloid and warty carcinomas, and lesser prevalent in keratinizing variants, such as verrucous, papillary and usual carcinomas (Guimarães et al., 2011). Before understanding the relationship between HPV and specific

Human Papillomavirus Infection and Penile Cancer: Past, Present and Future

http://dx.doi.org/10.5772/55811

229

Squamous cell carcinoma of the penis is currently divided in 12 subtypes. Each one of this subtypes shows distinctive outcomes, and this high number of subtypes makes its difficult to characterize the disease. About half of penile cancers are of the usual squamous histology,

**Basaloid carcinomas:** represent 4-10% of penile tumors. Macroscopically, these tumors show an ulcerative aspect, presenting as a solid, firm invasively neoplasm, with necrosis foci. Microscopically, they present a nesting pattern, with each nest presenting a solid or central necrotic nest (comedonecrosis). Keratinization can be observed, although not pathognomonic. Cells presents as small, basofilic, basaloid, spindle or pleomorphic, with abundance of mitotic

**Warty carcinomas:** represent 7-10% of all cases. It can be described as verruciform tumors, with an exoendophytical appearance, although a rare non-invasive exophytic tumor may be found. Histologically, a classical condylomatous papilla is observed, with a arborescent pattern, a central fibrovascular core, and keratinized cells, with presence of superficial and deep pleomorphic koilocytosis. Different from giant condillomas, in warty carcinomas these cells are typically malignant. Also, as a differential diagnosis, low-risk HPV or negative p16INK4a status favors a condilloma diagnosis. Prognosis is often good, with no signs of nodal involvment, although it might be present in deep invasive warty carcinoma (Chaux & Cubilla,

**Verrucous carcinomas:** represent 3-8% of the cases. Macroscopically are classically character‐ ized by exophytic, verrucoid white lesion, with a clear base separating them from the stroma. Microscopically, they are acanthotic, papillomatous neoplasms, with a high degree of difer‐ entiation. As most well differentiated tumors, they have a good prognosis, only presenting metastasis when they present areas with poor differentiation. However, if it presents large areas of undifferentiation, the tumor is classified as a mixed verrucous carcinoma, as the

**Papillary carcinoma:** represent 9-10% of all cases. It is also a verruciform tumor, diagnosed after excluding the possibility of a verrucous or warty tumor. Macroscopically is observed as an exophytic large tumor, with a clear jagged interface with stroma. Microscopically, papillo‐ matosis is observed and a low-grade histology is present. Different from verrucous carcinoma,

histological subtypes, a basic knowledge of penile cancer histology is required.

and apoptotic figures. Perineural and vascular invasions are often seen.

classical verrucous carcinoma is a classicaly well differentiated tumor.

while the rest is divided through the special types.

2012).

**Figure 3.** Representation of normal and HPV-infected epithelium according to the cellular differentiation and the dif‐ ferentiation-dependent viral functions (Adapted from Hebner & Laimins, 2006).

This provides an important microenvironment for cellular growth aberrations, and is partic‐ ularly important in penile pre-neoplastic lesions. Several authors have reported a higher level of HPV detection in PIN, when compared to penile cancer, open field for a HPV importance in the development of tissue growth abnormalities, leading to a soil field for carcinogenesis. In this model, HPV would be an important co-factor in penile pre-neoplastic development. Due to all of his effects in cell growth and lack of cell cycle control, the formation of lesions such as PIN associated to other important factors in penile carcinogenesis (genera hygiene, phimosis, chronic inflammation, high number of sexual partners).
