PTLDs arise after solid organ and hematopoietic stem cell transplants, with occurrences linked to immunosuppressive therapy and EBV status. Initial treatment typically involves reducing immunosuppressive therapy and using rituximab, with further options including immunochemotherapy or adoptive cellular therapy for refractory cases. Now, the inventors hypothesized that the concentration of sCD95L could exert a biological function and affect clinical outcomes by modulating the immune response. Using the K-VIROGREF cohort, they dosed by ELISA sCD95L in 175 transplant patients with PTLD and 16 transplant controls. Plasma levels of sCD95L were elevated in transplant recipients. Interestingly, in patients with PTLD who expressed higher concentrations of sCD95L, clinical outcomes were better than those with lower concentrations, especially in patients with central nervous system (CNS) involvement where sCD95L was a marker of good prognostic. Thus, sCD95L is a novel prognostic marker that might guide treatment strategies in patients with PTLD, especially in those with CNS involvement. Therefore, the present invention relates to the use of soluble CD95L as a prognostic marker in post-transplant lymphoproliferative disorders.