Naevi in allogeneic bone marrow transplantation recipients: the effect of graft-versus-host disease on naevi

Background Non-melanoma skin carcinoma is more common in transplant recipients, probably because of immunosuppression. An increased risk of developing melanoma could be a late effect of transplantation. The number of naevi, which is a risk marker for melanoma, is increased in renal transplant recipients of all ages and may be related to immunosuppression. The risk of melanoma has been suspected to be particularly high after bone marrow transplantation. Cutaneous graft-versus-host disease (GVHD) might be an interesting model for the study of interactions between naevi and the immune system. Objectives To assess whether aBMT exposes an individual to a particularly high risk of melanoma, using naevi as a surrogate measure of the risk. To improve our knowledge of the effect of the immune system on naevi, using GVHD as a model. Methods We carried out an epidemiological case-control study with two age-, sex- and hair colour-matched controls for each case. The results were analysed with analysis of variance, a general linear model analysis and multivariate analysis. Results The number of naevi was not significantly increased in aBMT patients, as compared with controls, although there was a significant excess on the palms and legs. In exploratory subgroup case-control comparisons and with the general linear model, patients who were conditioned with a combination of two alkylating drugs at high doses, and patients who had an aBMT before the age of 20 years tended to have a higher count of naevi (P = 0.002 and P = 0.06, respectively). Conversely, there was a trend in favour of a lower count of naevi in patients with diffuse skin lesions of chronic GVHD (P = 0.01). These data were corroborated by multivariate analysis, which showed that conditioning with high-dose chemotherapy, the absence of severe chronic cutaneous GVHD and a young age at transplantation were the main variables that independently predicted an excess of naevi. Conclusions This study of aBMT patients confirms that chemotherapy stimulates naevus growth. It also suggests for the first time that diffuse lesions of chronic cutaneous GVHD are associated with a decreased number of naevi. Whether allo-immunity, chronic skin inflammation or the masking of naevi by pigmentation and fibrosis is responsible for the decreased number of naevi requires further investigation. With respect to the long-term risk of melanoma in aBMT recipients, our results support an increased risk particularly when aBMT is performed at a young age, and when conditioning is with high doses of alkylating drugs.