Unusual presentation of extranodal diffuse large B-cell lymphoma in a solid-organ recipient during long-term immunosuppressive treatment.

INTRODUCTION: Posttransplant lymphoproliferative disorders (PTLDs) refer to a group of diseases, including diffuse large B-cell lymphoma (DLBCL), that develop after solid organ transplantation or hematopoietic stem cell transplantation. Extranodal involvement in PTLDs is common. Reports about exclusive bone marrow involvement are rare. CASE DESCRIPTION: A 70-year-old woman, who had undergone kidney transplantation in 2018, was diagnosed with exclusively extranodal, Epstein-Barr virus-negative DLBCL, with bone marrow and spleen involvement, during long-term immunosuppression. She achieved complete remission with combined immunochemotherapy and temporary hold of immunosuppression. CONCLUSIONS: This case shows an uncommon clinical presentation of DLBCL, which was challenging to diagnose, being entirely extranodal. The favorable clinical course relied on timely diagnosis and a multidisciplinary approach. Long-term consequences of posttransplant immunosuppression require a high level of suspicion for an appropriate management, aimed at preserving the graft while eradicating the lymphoproliferative disorder.