Objective:

To report a case of a patient with coexisting diffuse large B-cell lymphoma (DLBCL) and splenic peripheral T-cell lymphoma (PTCL) and highlight the diagnostic challenges associated with discordant lymphomas.

Approach:

• Patient Presentation: A 71-year-old man presented with fever, lymphadenopathy, splenomegaly, anemia, and thrombocytopenia.
• Initial Diagnosis: Bone marrow and immunohistochemistry confirmed stage IVB DLBCL, non-germinal-center B-cell-like subtype.
• Treatment and Response: The patient received dose-reduced R-CHOPE chemotherapy, achieving partial remission but persistent thrombocytopenia and splenomegaly.
• Surgical Intervention: Splenectomy was performed for suspected hypersplenism, revealing peripheral T-cell lymphoma.
• Subsequent Findings: A right zygomatic-orbital lesion later confirmed recurrent DLBCL.

Key Findings:

• The patient had coexisting DLBCL and splenic PTCL, identified through ongoing symptoms.
• Persistent splenomegaly and cytopenia indicated the need for repeat tissue sampling.
• Distinct immunophenotypes and splenic T-cell clonality supported the diagnosis of lineage-discordant lymphoma.

Interpretation:

Persistent or anatomically discordant disease manifestations should not be assumed to represent the initially diagnosed lymphoma subtype.

Limitations:

• The case highlights the rarity of composite and discordant lymphomas, making diagnosis challenging.
• Limited literature exists on splenic T/NK-cell lymphoma compared to B-cell lymphoma.

Conclusion:

This case emphasizes the importance of reevaluating lymphoma diagnoses in the presence of atypical clinical manifestations.