Clinicopathological spectrum and outcomes of biopsy-proven post-transplant lymphoproliferative disorder after kidney transplantation.

BACKGROUND/AIM: Post-transplant lymphoproliferative disorder (PTLD) is a malignancy that has gained increasing importance in transplantation practice due to the rising frequency of transplant procedures and the widespread use of immunosuppressive therapies. This study aimed to evaluate the clinical, laboratory, and treatment characteristics, as well as survival outcomes, of patients diagnosed with post-transplant PTLD following kidney transplantation. MATERIALS AND METHODS: In this retrospective study, a total of 21 patients who underwent kidney transplantation between 1977 and 2025 and were subsequently diagnosed with PTLD were analyzed. Demographic data, primary kidney diseases, transplant characteristics, immunosuppressive regimens, PTLD subtypes, laboratory parameters at diagnosis, treatment approaches, and follow-up outcomes were assessed. Patient survival was evaluated, and exploratory analyses of selected prognostic indicators were performed. RESULTS: The mean age of patients diagnosed with PTLD was 48 ± 15 years, and 38.1% were female. The most common PTLD subtype was diffuse large B-cell lymphoma (DLBCL) (66.7%). Extranodal involvement was present in 81% of patients. The median follow-up duration after PTLD diagnosis was 18 months (3-43). In univariate Cox regression analysis, sex, age at transplantation, age at diagnosis, clinical and laboratory parameters, donor characteristics, immunosuppressive therapy, and clinical scores including the renal-PTLD index and Hemoglobin, albumin, lymphocyte, and platelet (HALP) score, were not significantly associated with overall survival. International Prognostic Index (IPI) data were available for only 12 of 21 patients (8 low-risk and 4 high-risk). In this small subgroup, higher IPI category showed a trend toward increased mortality risk in univariate analysis (HR: 8.047; 95% CI: 0.830-77.996; p = 0.072). Exploratory Kaplan-Meier analysis showed shorter estimated median survival in the high-IPI group than in the low-IPI group (3 months [95% CI: 0-8.4] vs. 42 months [95% CI: 13.6-70.4]; log-rank p = 0.029); however, this finding was based on a limited number of patients. CONCLUSION: PTLD is a rare but serious complication following kidney transplantation, associated with substantial morbidity and mortality. Although this study was not powered to identify definitive prognostic factors, exploratory analyses suggested shorter survival among patients with higher IPI categories, supporting further evaluation of IPI in larger multicenter cohorts.