Case Report: Discordant diffuse large B-cell lymphoma and splenic peripheral T-cell lymphoma revealed by persistent splenomegaly and cytopenia.

Discordant lymphomas involving mature B-cell and T-cell neoplasms are uncommon and may be missed when atypical clinical manifestations are attributed to a known aggressive lymphoma. We report a 71-year-old man who presented with fever, generalized lymphadenopathy, splenomegaly, splenic infarction, anemia, and thrombocytopenia. Bone marrow, flow cytometry, and tissue immunohistochemistry supported stage IVB diffuse large B-cell lymphoma (DLBCL), non-germinal-center B-cell-like subtype, with bone marrow involvement. After dose-reduced R-CHOPE chemotherapy, partial remission was achieved, but thrombocytopenia and marked splenomegaly persisted. Splenectomy, performed for suspected hypersplenism, unexpectedly showed peripheral T-cell lymphoma with loss of B-cell markers and clonal TCRG and TCRB rearrangements. Ten months after presentation, a right zygomatic-orbital soft tissue lesion was biopsied and confirmed recurrent DLBCL. The patient received R-GemOx plus zanubrutinib, intrathecal chemotherapy, and later R-ICE plus zanubrutinib; however, repeated relapse occurred, and he died 33 months after initial presentation. This case illustrates that persistent splenomegaly, cytopenia, splenic infarction, or anatomically discordant progression during lymphoma treatment should trigger repeat tissue sampling and integrated pathological reassessment. The distinct anatomical distribution, lineage-specific immunophenotypes, and splenic T-cell clonality supported the diagnosis of lineage-discordant lymphoma.