I stumbled across this review article (first full reference below) earlier this week.
Two hundred patients developed a first NMSC after a median follow-up of 6.8 years after transplantation. The 3-year risk of the primary NMSC was 2.1%. Of the 200 patients with a primary NMSC, 91 (45.5%) had a second NMSC after a median follow-up after the first NMSC of 1.4 years (range, 3 months to 10 years). The 3-year risk of a second NMSC was 32.2%, and it was 49 times higher than that in patients with no previous NMSC. In a Cox proportional hazards regression model, age older than 50 years at the time of transplantation and male sex were significantly related to the first NMSC. Occurrence of the subsequent NMSC was not related to any risk factor considered, including sex, age at transplantation, type of transplanted organ, type of immunosuppressive therapy, histologic type of the first NMSC, and time since diagnosis of the first NMSC. Histologic type of the first NMSC strongly predicted the type of the subsequent NMSC
1. Nonmelanoma skin cancer in inflammatory bowel disease: A review; Millie D. Long, Michael D. Kappelman and Clare A. Pipkin; Inflammatory Bowel Diseases Volume 17, Issue 6, pages 1423–1427, June 2011; Article first published online: 25 OCT 2010 | DOI: 10.1002/ibd.21484
2. National Cancer Institute; Skin Cancer