INTRODUCTION
Basal cell carcinoma (BCC) is the most common form of cancer in the Caucasian population. In Australia, for example, BCC is more common than all other cancers (excluding squamous cell carcinoma [SCC] of skin) combined. With a population of 20 million, Australia reports that an estimated 246,000 people have at least one BCC treated every year and, due to the occurrence of multiple BCC in many patients, the annual incidence of treated BCC is 884 per 100,000. Fortunately, BCC is a relatively nonaggressive tumor that while locally invasive and destructive to local tissues, rarely metastasizes or is a cause of death.
PATHOGENESIS
UV exposure
As with the general population, the development of posttransplant BCC and SCC is affected to varying extents by different patterns of ultraviolet (UV) exposure. Cumulative lifetime sun exposure has not been shown to increase the risk of posttransplant BCC. However, the development of BCC is linked to increasing numbers of actinic keratoses, markers of solar damage, at or before transplantation. Intermittent intense sun exposure, including number of sunburns in childhood, appears to be a much more significant risk for posttransplant BCCs. Individuals with more sensitive skin phototypes are more likely to develop BCCs, with rates as much as 5.7 times higher in one report.
Immunosuppression
The duration and type of immunosuppression appear to bear a less direct relationship to BCC development, compared with that of SCC. The cumulative immunosuppressive drug dose did not affect BCC incidence in one study.