Current knowledge of immunosuppression as a risk factor for skin cancer development.

This review outlines our current understanding of the relationship between immunosuppression and skin cancer. Primary immunodeficiencies increase the incidence of skin cancer, but due to their low frequency, the establishment of accurate risk ratios remains lacking. Regarding secondary immunosuppression, available data demonstrate a significant increase of skin cancer in solid organ recipients, being the most common malignancy of this population. Immunosuppressive drugs have an important role in these patients, with an impact related to both the cumulative dose and the type of regimen used. The association of skin cancer and immunosuppressive drugs in non-transplant patients is conflictive for most of the drugs except for azathioprine. Many cancers lead to secondary immunosuppression as a mechanism for tumor growth and advancement, increasing the risk of progression of the primary tumor. Novel insights related with tumorigenesis and immune-escape mechanisms have led to promising new treatments in melanoma and squamous cell carcinoma.