CD Markers

Topic Completed: 1 February 2014

Revised: 13 December 2018, last major update February 2014

Copyright: (c) 2003-2018,, Inc.

PubMed Search: CD20[title]

Nat Pernick, M.D.
Page views in 2018: 7,707
Page views in 2019 to date: 4,685
Cite this page: Pernick N. CD20. website. Accessed July 18th, 2019.
Definition / general
  • Common B cell marker (also CD19, CD79a, PAX5)
  • Also called L26, membrane spanning 4 domains (MS4A1)
  • 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
Uses by pathologists
Case reports
Microscopic (histologic) images

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Images hosted on PathOut server:

Contributed by Andrey Bychkov, M.D., Ph.D.,
Kameda Medical Center

MALT lymphoma

Lymph node: angiomyomatous hamartoma

Skin: halo nevus

Burkitt lymphoma
of ileocecal valve
(contributed by Dr.
Kaveh Naemi, California)

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-)



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Bladder: follicular cystitis

Lymph node: infarction

lymphoma / Waldenström
(brain, fig D)

MALT lymphoma of liver (left), lung (right)

Diffuse large B cell lymphoma:


Breast (right)




Nasal cavity (fig 3A)

Ovary (fig 3)


Skin (fig D)

Other leukemia / lymphoma:

B-ALL (mature) of bone
marrow (fig 2: inset)

Bone marrow infiltration by
unspecified B cell lymphoma (fig C)

Follicular lymphoma

Neoplastic T cells (fig B)

Hairy cell leukemia

Hodgkin lymphoma: left-lymphocyte predominant cells are CD20+ (figs C&D); right-fig C

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:

Immunoblastic myofibroblastic tumor (reactive B cells, fig 2d)

Thymoma, ectopic
hamartomatous (fig C)

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
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
Flow cytometry images

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Hairy cell leukemia variant (fig A):
CD20 (bright) and CD22+

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