Organ transplant recipients receiving immunosuppressive therapy are prone to skin cancers, especially squamous cell carcinomas on sun-exposed areas. The frequency of skin cancers increases with time after transplantation, reaching 40 to 70% of patients after 20 years. Squamous cell carcinomas tend to be multiple and may have a life-threatening course. They are often associated with warts, premalignant keratoses, Bowen's disease and keratoacanthomas. Repeated excisions of tumours and sessions of cryotherapy are not always satisfactory, as they lead to numerous scars and aesthetic impairment.
Systemic retinoids may be used in organ transplant recipients without inducing graft rejection; they prevent the occurrence of dysplastic lesions and skin carcinomas. There is usually relapse following discontinuation of retinoids, raising the question of continuous or intermittent treatment. The long term use of retinoids may be limited by adverse effects which are cumulative with those of immunosuppressive treatment. Hence, systemic retinoids should be reserved for patients developing a great number of lesions over short periods.
Topical retinoids probably represent the best way to control the proliferation of premalignant and malignant lesions. Further studies are required to assess the efficacy and safety of new retinoids.