CD20 positive T cell lymphoma: is it a real entity?

Area of Science:

• Hematology
• Oncology
• Immunophenotyping

Background:

• CD20-positive T cell lymphoma is a rare entity encompassing precursor and peripheral T cell types.
• Diagnostic challenges arise due to potential misclassification as B cell lymphoma, leading to clinical implications.

Observation:

• A unique case of nodal CD20-positive T cell lymphoma with concurrent cutaneous and subcutaneous involvement is presented.
• Both nodal and cutaneous lesions exhibited identical monoclonal bands on T cell receptor rearrangement assay.
• Notably, the skin lesion lacked CD20 expression, indicating antigen instability.

Findings:

• The T cell receptor rearrangement assay confirmed a monoclonal T cell process in both nodal and cutaneous sites.
• CD20 expression was present in the nodal lymphoma but absent in the cutaneous involvement.
• The instability of CD20 antigen suggests it may not be a critical component of the tumor's immunophenotype or clinical behavior.

Implications:

• CD20 positivity in T cell lymphoma can lead to diagnostic confusion with B cell lymphomas.
• The instability of CD20 expression highlights the importance of comprehensive diagnostic techniques beyond initial immunophenotyping.
• Understanding CD20 antigen variability is crucial for accurate diagnosis and management of rare T cell lymphomas.