INTRODUCTION

Immunodepleted patients are at higher risk for developing lymphoproliferative disorders (LPD), above all non-Hodgkin's lymphomas (NHL). Even though the association between primary immunodeficiency diseases (e.g. X-linked lymphoproliferative syndrome, common variable immunodeficiency, ataxia telangiectasia and Wiskott–Aldrich syndrome) and LPDs, on the one hand, and between LPDs and autoimmune diseases, on the other, is well known, the leading causes of immunosuppression are considered at present to be organ transplantation and HIV infection. Generally, lymphomas in immunocompromised hosts differ from lymphomas in the general population in histopathological findings, increased extranodal involvement, a more aggressive clinical course, poorer response to conventional therapies and poorer outcome.

In patients who undergo solid-organ transplantation, the risk for lymphoma is strongly influenced by the type of organ transplanted: during the first year after kidney or heart transplantation it is 20 and 120 times higher, respectively, than in the general population. The majority of lymphomas develop within the first three months after transplantation, even if some cases are reported after prolonged immunodepression. Overall the risk of cancer in organ-transplant recipients is well known: the frequency of cancer after renal transplantation was reported to be 6% in the United States and 8.3% in the Nordic countries, that is 4.5–6.3 times higher than in the general population. In a large series of 1844 renal-transplant recipients in Italy a significantly increased incidence of Kaposi's sarcoma, cancers of the lip, liver and kidney, and NHL was observed.

The incidence of HIV-related NHLs (HIV-NHL) has increased since 1981.