This is a multicentric observational retrospective cohort study of patients with histological diagnosis of PTLD.

The aim of the study is to analyze the clinical features and survival of patients who received a PTLD diagnosis with the target to assess a survival outcome, to obtain an epidemiologic and clinical characterization of the subpopulations affected by PTLD, to recognize unfavorable properties, to report the current treatment strategies, to provide rationale for the design of a prospective registry in order to develop future novel treatments.

This is a multicentric observational retrospective cohort study of patients with histological diagnosis of PTLD. Retrospective data will be collected for all cases of PTLD diagnosed during a 10 years period since 1st January 2011 to 31th December 2021.

The following clinical characteristics of the patient at the time of PTLD diagnosis and pathology will be taken into consideration: positivity of EBV virus, serum LDH concentration, PTLD subtype (early lesion, polymorphic or monomorphic PTLD), lymphoma histotype, stage of disease according to the Ann Arbor classification and localization (nodal or extranodal), immunosuppressive regimen taken by the patient since the transplant, therapeutic approach adopted, and response obtained.

Inclusion Criteria:

• histological diagnosis of PTLD obtained from a biopsy sample (availability of stocked biopsy sample is requested but not mandatory);
• age over 18 years at time of diagnosis of PTLD;
• previously subjected to allogeneic transplantation (both SOT and HSCT);
• diagnosis of PTLD obtained in 10 years' time frame (from 01/01/2011 to 31/12/2021);
• free and voluntary written informed consent (included unreachable subjects according to Art. 36 UE Regulation 2016/679 and to the current Italian Privacy Regulation).

Exclusion Criteria:

• Patients not meeting the above-mentioned inclusion criteria.

Population will be composed by patients with histological diagnosis of PTLD. The following clinical characteristics of the patient at the diagnosis of PTLD and pathology will be taken into consideration: positivity of EBV virus, serum LDH concentration, PTLD subtype (early lesion, polymorphic or monomorphic PTLD), lymphoma histotype, stage of disease according to the Ann Arbor classification and localization (nodal or extranodal), immunosuppressive regimen taken by the patient since the transplant, therapeutic approach adopted and response obtained.