Peripheral T-cell lymphoma with aberrant expression of CD79a and CD20: a diagnostic pitfall

Area of Science:

• Hematopathology
• Oncology
• Immunology

Background:

• Immunohistochemistry is crucial for lymphoma diagnosis, guiding prognosis and therapy.
• Lymphomas are classified by cell lineage, with distinct clinical behaviors.
• Accurate lineage assignment is essential for effective patient management.

Observation:

• A case of peripheral T-cell lymphoma presented with unusual coexpression of B-cell antigens CD20 and CD79a.
• Tumor cells also expressed T-cell markers (CD3, CD8, CD43, TIA-1) and CD56, S-100.
• BetaF-1 staining was negative on tumor cells, suggesting a potential gamma/delta T-cell origin.

Findings:

• Molecular studies confirmed clonal T-cell receptor gamma chain gene rearrangement, establishing T-cell lineage.
• Immunoglobulin heavy chain gene rearrangement was absent, ruling out B-cell lineage.
• The coexpression of both T- and B-cell markers in mature T-cell malignancies is rare and poses diagnostic challenges.

Implications:

• This case underscores that no single marker guarantees absolute lineage specificity in lymphomas.
• Immunophenotypic analysis requires comprehensive panels of antibodies for accurate diagnosis.
• Ambiguous lymphoma phenotypes may necessitate genotypic studies for definitive lineage assignment.