Test Catalog

Test ID: CD20I    
CD20 Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Classification of lymphomas

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

CD20 is a phosphorylated protein preferentially expressed by mature B lymphocytes. CD20 is not expressed by most normal plasma cells. It is one of the most specific B-cell lineage-associated antigens used in the diagnosis of B-cell lymphomas.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation; only technical performance of the stain is performed. If an interpretation is required, order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request; call 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen-dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Choi CH, Park YH, Lim JH, et al: Prognostic implication of semi-quantitative immunohistochemical assessment of CD20 expression in diffuse large B-cell lymphoma. J Pathol Transl Med. 2016;50(2):96-103 doi:10.4132/jptm.2016.01.12

2. Duman BB, Sahin B, Ergin M, Guvenc B: Loss of CD20 antigen expression after rituximab therapy of CD20 positive B cell lymphoma (diffuse large B cell extranodal marginal zone lymphoma combination): A case report and review of the literature. Med Oncol. 2012;29:1223-1226 doi:10.1007/s12032-011-9955-3

3. Cang S, Mukhi N, Wang K, Liu D: Novel CD20 monoclonal antibodies for lymphoma therapy. J Hematol Oncol. 2012;5:64 doi:10.1186/1756-8722-5-64