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

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. 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. 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.