On the basis of clinical and epidemiologic evidence, there can be little doubt that UV radiation is the predominant causal factor in cutaneous carcinogenesis in humans.1,2 Equally, work with laboratory animals has clearly demonstrated that skin cancer is associated with a failure of the immune system to recognize tumor antigens and/or to destroy malignant cells.3 In this context, UV-induced skin cancers may be viewed as the end result of a confrontation in which cutaneous and systemic elements of the immune system begin as coconspirators for tumor destruction, and end in a failure of surveillance and defense.
In this month's issue of the Archives, Alcalay et al4 present observations concerning aberrations in the appearance and distribution of Langerhans' cells (LCs) in the epidermal components of squamous cell carcinomas. Their findings suggest that epidermal LCs, which are considered the outermost sentinels of the immune system, play a relevant role