Our study shows that BCCs developing in OTRs show some significant differences compared with their "ordinary" counterparts appearing in nonimmunosuppressed patients. On average, BCCs develop in OTRs at a significantly younger age (15 years earlier) than in the general population. This trend—which was more pronounced for kidney than heart transplant recipients—has also been observed for other epithelial malignancies, including actinic keratoses,24 SCC,25 and Merkel cell carcinoma,26 and could be due to the immunosuppressive treatment acting as a tumor promoter. As previously reported,27 we did not observe any BCC in children who had undergone transplantation; however, one of the younger OTRs with BCC (aged 29 years at the time of BCC diagnosis) had undergone several renal transplantations during childhood, and it can be speculated that such patients may be at higher risk for BCC development because of the longer period of immunosuppression. The preponderance of BCC in men, found in our control group, proved to be even higher in OTRs, further supporting the contention that male sex is a risk factor for skin carcinomas in general.6,12,14,15,28,29 Another remarkable difference between BCCs in controls and OTRs concerns their anatomic distribution: although in both groups BCCs appear predominantly over the head and neck, the proportion of BCCs developing in extracephalic locations in OTRs was significantly higher than that in controls. In our group of OTRs, the most frequent BCC location was the back, which was as frequent as the nose (that was also the most common location in controls). We also found some BCCs on unusual (sun-protected) sites in OTRs,30 such as the genitalia, hand, or axilla, that were not found in controls. These findings are in keeping with previous observations5,31 and suggest that sun exposure may play a lesser role in the development of BCC in OTRs in comparison with the general population. Risk factors specific to OTRs, such as immunosuppression and possibly human papillomavirus infection,32 seemingly substitute in these patients for the role that ultraviolet radiation plays in nonimmunosuppressed patients. In BCC in OTR, we did not observe obvious histologic signs of human papillomavirus infection (data not shown), but the demonstration of viruses within malignant tumors requires more sensitive detection techniques, such as molecular biology. However, several patients had concomitant or preceding viral warts, suggesting that HPV may have played a role in the development of BCC. Because of their possible unusual locations, BCCs may be clinically misleading in OTRs; therefore, lesions located on non–sun-exposed sites should not be overlooked but examined histologically in case of doubt. In this study, BCCs appeared on average 6.9 years after transplantation, sooner after liver or heart than after kidney transplantation. This delay was even shorter in some studies,19 probably because of the type of organ grafted; indeed, like other skin tumors, BCCs tend to develop earlier in heart (compared with kidney) transplant recipients, probably because of the older age of these patients at the time of grafting11 and possibly also because of the higher immunosuppressive treatment used after heart compared with kidney transplantation. In our study, kidney transplant recipients accounted for the majority (63.7%) of OTRs.