[Melanoma in organ transplant patients]

The incidence of cutaneous melanoma has rapidly increased in the white population over the last decades. It has been estimated that the incidence doubles world-wide every 10 years. Different risk factors have been identified, including immunosuppression. The aim of our study-was to determine the relative risk of developing melanoma in the organ transplant population and the clinical and histological features of their melanomas.

This retrospective study was conducted with the collaboration of 9 University Hospital Centers: Besançon, Brest, Caen, Dijon, Lille, Lyon, Nantes, Paris (Pitié-Salpétrière) and Rennes. A questionnaire was sent to the different departments of dermatology of these hospitals to obtain information on patients who had presented a melanoma after a transplantation between 1971 and 1997. During this period, there were 12,477 organ transplant recipients in the transplantation units of these 9 hospitals. Average follow-up for these patients was about 5 years and the average duration of immunosuppressive therapy was about 4.5 years.

Among 12,477 organ transplant recipients, we found 17 cases of melanoma but no data could be obtain on one case: 14 occurred in renal transplant recipients and 3 in cardiac transplant recipients. Clinical and histological data were only available in 16 patients. The average time between transplantation and diagnosis of melanoma was 63 months, but it was 5 times shorter for 2 patients who had a past history of melanoma before transplantation. Two patients had a mucosal melanoma; for the cutaneous melanomas, 2 appeared on Dubreuilh melanosis, 2 were in situ melanomas, 7 were superficial spreading melanomas and 3 were nodular melanomas. The histological review of 11 cutaneous melanomas revealed a precursor nevus in 6 cases and a weak or no stroma reaction in 7/7 cases. Complete excision of the melanoma was performed in all patients except one with anorectal melanoma. Four patients died of visceral metastasis within a mean 15 months. The other 12 patients are still alive with a mean 3 year course since tumor treatment. We tried to determine the relative risk of developing melanoma in the renal transplant population (14 cases). The number of expected cases of melanoma was 5.54, giving a relative risk of 2.5.

Only 4 studies have shown an increase in the incidence of melanoma in the renal transplant population: approximately 2 to 5-fold. In our study, the 2.5-fold increase in melanoma was estimated with an average 5 year follow-up and an average 5 year immunosuppressive therapy. This is probably an underestimation of risk because we were unable to make an exhaustive collection of cases of melanomas even though transplant recipients undergo more physical examinations than a reference population. The mean latency period from transplantation to melanoma diagnosis was 63 months, as in other studies. Histological examination showed that a precursor nevus is frequent with weak host cellular response to the tumor. The prognosis of these melanomas remains difficult to predict, but in our study, it would not appear to be as poor as expected. Discontinuation of immunosuppressive therapy would not appear to be necessary except in the presence of metastasis. Finally, our study demonstrates the importance of good patient follow-up, even after graft rejection due to the persistent risk of melanoma.