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Lymphoproliferative disorders arising under immunosuppression with FK 506: initial observations in a large transplant population.

POSTTRANSPLANT Iymphoproliferative disorders (PTLDs) encompass a range of benign to frankly malignant lymphoid tumors that occur in the immunocompromised state.1 Many, but not all, are of B-lymphocyte origin and the Epstein-Barr virus is acknowledged to be an important cofactor in most cases. 
 
The introduction of cyclosporine A (CyA) in the early 1980s brought with it concerns that this new immunosuppressant might also cause an inevitable increase in the number of transplant lymphomas.2 These fears were not borne out, and PTLDs presently occur in about 2% of transplant recipients. 
 
FK 506 is a new macrolide immunosuppressant that has been shown to be at least 100 times more potent than CyA by in vitro assays.3,4 It is appropriate, therefore, to again ask whether or not the degree of immunosuppression exerted by such a powerful new drug carries with it an unacceptable price in the form of increases in the frequency or aggressiveness of transplant-associated lymphomas.