Abstract
Primary bone marrow (BM) diffuse large B-cell lymphoma (PBM-DLBCL) is an extremely rare and highly aggressive subtype of extranodal lymphoma. Its non-specific clinical manifestation, often presenting with pancytopenia, poses significant diagnostic challenges, frequently leading to misdiagnosis as other hematological disorders. In April 2023, a 70-year-old man was hospitalized in the Department of Hematology of The First Affiliated Hospital of Jishou University (Jishou, China). The patient presented to the hospital with fever, malaise and severe pancytopenia. An initial BM biopsy indicated a T-cell lymphoproliferative disorder accompanied by myelofibrosis (MF), for which empirical immunosuppressive therapy was administered without clinical benefit. A total of 10 months later, a repeat BM biopsy demonstrated a distinct population of CD20+ and CD79a+ large B-cells, establishing a definitive diagnosis of PBM-DLBCL with secondary MF. The patient declined further therapeutic interventions and was lost to follow-up thereafter. The present case report underscores the diagnostic challenges of PBM-DLBCL, which can mimic other marrow pathologies. The report highlights the critical importance of repeat BM biopsies in cases of refractory or unexplained pancytopenia. The potential mechanisms linking DLBCL with secondary MF are also discussed, emphasizing the need for heightened clinical vigilance to prevent misdiagnosis.