Epidemiology of keratinocyte carcinomas after organ transplantation

Keratinocyte carcinoma (KC) is the most common type of cancer among white populations, but it is even more common among solid organ transplant recipients (OTRs). The most frequent histological type of KC among OTRs is cutaneous squamous cell carcinoma (cSCC), followed by basal cell carcinoma, although the reverse is seen in the general population. Metastatic cSCCs are more frequent, and mortality is increased compared with immunocompetent populations. There is strong evidence that the risk of KC among OTRs rises with increasing time after transplantation and older age at transplantation, and that KC is enhanced in those with sun-damaged skin. This evidence suggests that accelerated accumulation of genetic damage from several sources leads to excess KC in OTRs. We describe international variation in KC and focus on trends in immunosuppressive regimens, the role of ultraviolet susceptibility and exposure, and the contribution of genetics to tumour development. Further epidemiological studies are needed to address gaps in our understanding of the mediation of excess KC by immunosuppressive drugs, viral infection, genetic susceptibility, timing of relevant ultraviolet exposure or some combination of these factors.