CD Markers
CD20
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: CD20[title]
CD20
Author: Nat Pernick, M.D.
Topic Completed: 1 February 2014
Minor changes: 16 November 2020
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: CD20[title]
Table of Contents
Definition / general | Pathophysiology | Clinical features | Uses by pathologists | Case reports | Microscopic (histologic) images | Positive staining - normal | Positive staining - disease | Negative staining | Flow cytometry descriptionCite this page: Pernick N. CD20. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cdmarkerscd20.html. Accessed January 25th, 2021.
Definition / general
Pathophysiology
- 33kd phosphoprotein with 3 hydrophobic regions that traverse the cell membrane, creating a structure similar to an ion channel that allows for the influx of calcium required for cell activation
- Initially expressed on B cells after CD19 / CD10 expression and before CD21 / CD22 and surface immunoglobulin expression; retained on mature B cells until plasma cell development
- Delivers early signal in B cell activation, allowing resting B cells to respond to later antigens
- Closely related to FMC7, which recognizes a CD20 epitope (Leukemia 2003;17:1384), particularly if there is strong CD20 expression (not in CLL, Am J Clin Pathol 2003;120:754)
Clinical features
- Rituximab is a chimeric murine-human anti-CD20 antibody used to treat B cell lymphomas; treatment may cause selection of CD20 negative (but CD79a+) tumor subclones (Am J Surg Pathol 2005;29:1399)
- Changes in morphology and CD20 expression after rituximab therapy vary widely (Am J Surg Pathol 2013;37:563)
- Rituximab is also used to treat autoimmune disorders (Clin Immunol 2005;117:207, J Clin Aesthet Dermatol 2013;6:45), TTP / HUS (Clin Transplant 2005;19:423, Blood Transfus 2010;8:203), ABO incompatible transplantation (Transplant Proc 2005;37:1205) and transplant rejection (Clin Transplant 2005;19:137)
- Radioimmunotherapy with Rituximab may be effective for follicular lymphoma (Clin Dev Immunol 2013;2013:875343) and as myeloablative therapy followed by autologous stem cell support for relapsed/refractory B cell lymphoma (Oncotarget 2013;4:899)
- Dim CD20 expression on IgG4 plasma cells in IgG4-related lymphadenopathy may explain efficacy of rituximab in IgG4-related disease (Arch Pathol Lab Med 2013;137:1282)
- Other anti-CD20 antibodies are also effective (Future Oncol 2013;9:1829, Br J Haematol 2013;162:693)
- CD20 antigen may be expressed by reactive or lymphomatous cells of transformed mycosis fungoides (Am J Surg Pathol 2013;37:1845); also other T cell lymphomas (see below under Positive stains)
- CD20 mutation rarely causes common variable immunodeficiency 5 (OMIM #112210)
- "Double hit" lymphomas show reduced CD20 expression by flow cytometry (Am J Clin Pathol 2010;134:258)
Uses by pathologists
- Commonly used B cell marker
- Not useful for diagnosis of bone marrow involvement by diffuse large B cell lymphoma (Appl Immunohistochem Mol Morphol 2009;17:93)
Case reports
- Large atypical cells of nodular lymphocyte predominant Hodgkin lymphoma (Case of the Week #284)
Microscopic (histologic) images
Scroll to see all images:
Contributed by Andrey Bychkov, M.D., Ph.D.
MALT lymphoma
Cases of the month, AFIP images
Lymph node: angiomyomatous hamartoma
Skin: halo nevus
Burkitt lymphoma
of ileocecal valve
Hodgkin lymphoma, nodular lymphocyte predominant subtype: small lymphocytes and LP cells are CD20+ but classic RS cells are CD20-
MALT lymphoma of stomach
Myeloid sarcoma of bone (negative)
NK/T cell lymphoma, nasal type (tumor cells are negative)
T cell lymphoma; right: fig A
Thymoma, lymphocyte predominant (CD20-)
Brain
Intravascular
Images hosted on other servers:
Nonneoplastic:
Bladder: follicular cystitis
Lymph node: infarction
MALT lymphoma of liver (left), lung (right)
Diffuse large B cell lymphoma:
Breast (right)
Mediastinum
Brain
Intravascular
Prostate
Other leukemia / lymphoma:
Bone marrow infiltration by
unspecified B cell lymphoma (fig C)
Follicular lymphoma
Neoplastic T cells (fig B)
Mantle cell lymphoma of prostate
Marginal zone lymphoma of prostate
T cell lymphoma
Posttransplantation lymphoproliferative disorder:
Liver; right side fig 3 is CD20
Other neoplasms:
Thymomas, various
Positive staining - normal
- Most B cells (considered a pan B cell antigen), also follicular dendritic cells
- Hematogones can be CD20+ and a panel is useful in distinguishing them from leukemia cells (Am J Clin Pathol 2000;114:66)
Positive staining - disease
- 90% of B cell lymphomas (Am J Clin Pathol 2006;126:534), although B cell lymphomas are CD20 negative after rituximab, and other B cell markers should be used
- 40% of pre B ALL / LBL
- Also spindle cell thymomas (Am J Surg Pathol 1992;16:988, Diagn Pathol 2007 May 11;2:13)
- 80% of nodular lymphocyte predominant Hodgkin lymphoma, 20% of classic Hodgkin lymphoma (may be an adverse prognostic factor, Br J Haematol 2004;125:701, PLoS One 2009;4:e6341)
- Dimly expressed in T cells (benign and neoplastic, particularly in bone marrow, Am J Surg Pathol 2008;32:1593, Am J Clin Pathol 1996;106:78, Am J Clin Pathol 1994;102:483), some myelomas (Mod Pathol 2004;17:1217, Blood 2003;102:1070) and occasionally acute myelogenous leukemia
- T cell lymphomas - rare (Acta Cytol 2005;49:365, Am J Hematol 2002;71:331, Am J Clin Pathol 1994;102:483, Mod Pathol 2001;14:105, Mod Pathol 2000;13:1244, but see J Clin Pathol 2004;57:442)
Negative staining
- Non-hematopoietic cells, most T cells, basophils, plasma cells and mastocytosis
- Note: staining does not work well with Bouin’s fixative
Flow cytometry description
- Brighter expression in follicular lymphomas than normal B cells (Am J Clin Pathol 2005;124:576)
