This study aimed to investigate whether the occurrence of cutaneous squamous cell carcinomas (SCCs) is associated with an increased risk of internal malignancies (IMs) in kidney transplant recipients (KTRs). In a cohort study, all patients receiving kidney transplantation in Leiden, the Netherlands, between 1966 and 2006 were followed up. All malignancies that had developed between 1966 and 2007 were recorded. Time-dependent Cox regression analyses were used to calculate the association between

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... the development of cutaneous SCCs and IMs. The incidence of IMs in the KTRs after transplantation was also compared with the general Dutch population by calculating standardized morbidity ratios (SMRs) and was matched for age, sex, and time period in which the malignancy had occurred. Among 1,800 KTRs, 176 (9.8%) developed cutaneous SCCs and 142 (7.9%) developed IMs after transplantation. In patients with prior cutaneous SCCs, the adjusted risk to develop IMs was 3.0 (1.9; 4.7). In KTRs without cutaneous SCCs, the risk of IM compared with the general population was hardly increased. KTRs with cutaneous SCCs have an increased risk to develop IMs, and this information can be used to identify KTRs who are at an increased risk for IMs.