INTRODUCTION

A wealth of information has been published in recent years concerning the incidence, clinicopathological spectrum, treatment, prognosis, and prevention of skin malignancies in organ transplant recipients (OTRs). However, relatively little has been reported in relation to benign skin tumors. This section will review the available published literature, together with unpublished data, relating to benign tumors observed in our own cohort of over 800 renal transplant recipients under long-term surveillance since 1989 at Bart's and the London NHS Trust, London, U.K (BLT). It should be emphasised that accurate prevalence data are limited for almost all of these tumors, and most published and unpublished observations should therefore be regarded as essentially anecdotal until further data are available from larger cohort studies. Nonetheless, an appreciation of the spectrum of benign tumors in OTRs is important, as some of these tumors may simulate more aggressive malignancies; others represent a source of considerable morbidity, and a few may possess potential for malignant transformation. Relevant published data are summarized in Table 17.1, and particular tumors are discussed in more detail in the following text.

KERATINOCYTE TUMORS

Squamous cell papillomas, verrucal keratoses

Viral warts (HPV-induced squamous cell papillomas) are, undoubtedly, the most prevalent benign keratinocyte tumor in OTRs, and these are dealt with elsewhere in the volume. However, another group of squamous cell papillomas that lack typical HPV-associated histopathological features are also well recognised in OTRs. Often referred to as verrucal keratoses, these lesions usually present as hyperkeratotic papules and nodules (Figure 17.1).