Aberrant CD20 Expression in Angioimmunoblastic T-cell Lymphoma

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We report on a 60-year-old man, having angioimmunoblastic T-cell lymphoma (AITL) with aberrant expression of CD20. The initial biopsy specimen showed features of AITL with the typical CD3⁺CD20^- immunophenotype. As the disease progressed, biopsy specimens of the recurrent lesions showed unusual results for AITL with the CD20⁺ immunophenotype in both flow cytometry and immunohistochemistry analysis. Double immunostaining confirmed that the lymphoma cells were simultaneously positive for CD3 and CD20. The disease became resistant to combined chemotherapies and the patient died 3 years after the initial diagnosis. Autopsy revealed a composite of AITL and EBV-positive diffuse large B-cell lymphoma. Although it is unknown whether the instability of the CD20 antigen expression is correlated with the behaviour of AITL, the administration of rituximab should be considered as an alternative therapeutic option in such cases.