Penile Intraepithelial Neoplasia PIN

The term penile intraepithelial neoplasia (PIN) is used to describe different premalignant penile lesions, and is often used interchangeably in the text with the term carcinoma in situ (CIS). It is not to be confused with the newer term PeIN in the more recently proposed classification systems.13 PIN presents in different clinico-pathological forms, and with differing degrees of dysplasia ranging from mild (PIN I) and moderate (PIN II), to severe (PIN III). PIN III is more synonymous with carcinoma in situ CIS, and is eponymously known as Erythroplasia of Queyrat and Bowen's disease. Both are essentially the same histological premalignant condition, differing primarily only in location.15 Lesions arising from the mucosal surfaces of the genitalia, such as the inner prepuce and glans, are called Erythroplasia of Queyrat (EQ), while Bowen's disease is essentially considered the same pathological process affecting the skin of the penile shaft.

Lesions which occur in Bowen's disease are usually solitary, well defined, scaly, dull-red plaques, often with areas of crusting (Fig. 5.1). Occasionally lesions may be heavily pigmented, resembling melanoma. While they primarily occur on the shaft, associated lesions are sometimes encountered in the inguinal and suprapubic region. Lesions may also occasionally have associated leukoplakic, nodular, or ulcerated changes.

Lesions in EQ are usually sharply defined plaques, which have a smooth, velvety, bright red appearance (Fig. 5.2). They are usually painless, but can have areas of erosion. The vast majority occur in uncircumcised men with phimotic foreskins.

HPV has a high prevalence in CIS, with reported rates of high-risk HPV-16 in approximately 80% of Bowen's disease cases 1 6 and 88% of EQ cases in small series.17 However, these two entities have differing rates of progression to invasive disease. Invasive SCC has been reported in 5% of cases of Bowen's disease,18 while EQ has reported transformation rates of up to 30%.1719 The exact cause for this difference is unclear; one theory is that the mucosal location of EQ is more susceptible to invasive transformation. Other theories surround possible different pathogenic

Fig. 5.1 Bowen's disease of the penis

Fig. 5.1 Bowen's disease of the penis

Fig. 5.2 Erythroplasia of Queyrat presenting in a 45-year-old uncircumcised male who noticed a progressive red area on the glans penis

processes related to co-infection with other HPV subtypes. A small series looking at HPV subtypes in eight patients with EQ found co-infection with HPV-8 in all cases, while no co-infection was detected in control patients with Bowen's disease.17 The effect of this co-infection on the invasiveness of EQ remains unclear. At present, there is no clear evidence linking aggressiveness of PIN based on the HPV types involved. In fact no study has clearly identified any difference in the transformation rate of PIN lesions based on the presence or absence of HPV infection, and more research into this field is required.

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