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Updated: Aug 9, 2026
A Syngeneic Mouse B-Cell Lymphoma Model for Pre-Clinical Evaluation of CD19 CAR T Cells
Published on: October 16, 2018
Cutaneous B-cell lymphoma with loss of CD20 immunoreactivity after rituximab therapy
Loren E Clarke1, Michael G Bayerl, W Christopher Ehmann
1Department of Pathology, The Pennsylvania State University College of Medicine/Hershey Medical Center, C7633 Hershey Medical Center (H083/Box 850), Hershey, PA 17033, USA. lclarke816@aol.com
Background:
Antibodies to the B-cell-specific antigen CD20 are widely used for immunohistochemical identification of B-cell lymphomas, approximately 95% of which are strongly CD20-positive.
Methods:
We report a 51-year-old male with a CD20-positive systemic B-cell lymphoma who developed a CD20-negative relapse with secondary cutaneous involvement after therapy with the anti-CD20 monoclonal antibody rituximab (Rituxan).
Results:
Biopsy of a skin nodule demonstrated an atypical lymphocytic infiltrate that was negative for CD20, CD3, lysozyme, and myeloperoxidase, but strongly positive for CD45rb (LCA) and the B-cell marker CD79a.
Conclusions:
We conclude that loss of CD20 expression in cutaneous B-cell lymphoma (both primary and secondary) is important to recognize, that immunohistochemistry for CD79a, another widely expressed B-cell marker, is useful in the identification of CD20-negative B cells in such cases, and that loss of CD20 expression may become more common, as use of rituximab is expected to increase.
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