Introduction

Abstract

Human melanoma is the most rapidly increasing malignant skin disease in Caucasians (Leiter and Garbe 2008). Once considered a rare disease, the lifetime risk for developing melanoma in the US has increased from approximately 1 in 1,500 during the 1930s to its present risk of approximately 1 in 60 (Giblin and Thomas 2007). The American Cancer Society’s recent cancer report estimates that 68,130 new cases of melanoma will be diagnosed and 8,700 deaths will result from melanoma during 2010 in the United States (American Cancer Society 2010). Important risk factors for developing melanoma include increased number of melanocytic nevi, a family history of melanoma, or a history of previous melanoma (Seykora and Elder 1996; Psaty et al. 2010). Prolonged sun exposure associated with increased outdoor activity has been suggested to play an important role in the epidemiologic increase in the incidence of melanoma (Leiter and Garbe 2008; Moan et al. 2008). Acute exposure of the skin to ultraviolet (UV) radiation can induce varying degrees of erythema, pigmentation, and impairment of immune function (Matsumura and Ananthaswamy 2004). Recently, increased numbers of melanocytic nevi associated with sunburn and intermittent or “holiday” sun exposure has been suggested as a major risk factor for developing melanoma in different studies (Elwood and Jopson 1997; Newton-Bishop et al. 2010). In fact, the Clark model for melanoma suggests a stepwise progression from hyperplastic and dysplastic nevi to melanoma (Fig. 1.1) (Clark et al. 1984).