CD Markers

Author: Nat Pernick, M.D. (see Authors page)

Revised: 18 November 2016, last major update February 2014

Copyright: (c) 2003-2016,, Inc.

PubMed Search: CD20[title]
Cite this page: CD20. website. Accessed July 21st, 2018.
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
Scroll down to see all images

Images hosted on Pathout server:

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-)


Bladder: follicular cystitis

Lymph node: infarction

Hodgkin lymphoma: Reed–Sternberg cells

Lymphoplasmacytic lymphoma /
Waldenström macroglobulinemia
(brain, fig D)

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

Diffuse large B cell lymphoma


Breast (right)




Nasal cavity (fig 3A)

Ovary (fig 3)


Skin (fig D)

Other leukemia / lymphoma

T cell lymphoma (fig D)

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 (fig 5)

Marginal zone lymphoma of prostate (fig 7)

T cell lymphoma; right: fig A

Post-transplantation 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

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